Class Cleavage and Left Electoral Mobilization: Theoretical Background

The concept of cleavage lies in path-breaking studies by Lipset and Rokkan (Reference Lipset, Rokkan, Lipset and Rokkan1967) and Rokkan (Reference Rokkan1970). However, notwithstanding their extensive use of the concept for the formulation of their genetic theory of party systems, Lipset and Rokkan do not provide a clear definition of cleavage, whose meaning has remained loose and has been used for a long time as a synonym of division and conflict. As Bartolini (Reference Bartolini2000, 16) puts it, the concept of cleavage is “either reduced down to that of social cleavage or raised up to that of political cleavage.” This is because the concept refers to both social structure and political order. Thus scholars often use the expression “social cleavage” or “political cleavage” depending on which aspect they want to emphasize.

In this regard, an important systematization comes from Bartolini and Mair (Reference Bartolini and Mair2007, 199). According to these authors, the concept of cleavage incorporates three elements: 1) the empirical referent of the concept, that is, the social group(s) arising from a conflict generated in the society, such as the working class (and, in reaction to it, the bourgeoisie) in the case of the class cleavage (empirical or socio-structural element); 2) a set of values and beliefs providing the social group(s) with a sense of identity and self-consciousness (cultural or normative element); and 3) an organizational structure (i.e., a political party) that coordinates and inspires the collective action of the social group and brings its interests into the political system (organizational element). This widely accepted definition resulting in the concept of cleavage involves at the same time socio-structural, ideological, cultural, organizational, and institutional elements. Therefore, it follows that a social conflict per se is not sufficient to have a cleavage. To be translated into a cleavage, a social conflict needs to generate a sense of identity and common beliefs and, most importantly, it needs to be politicized through the activity of an organization devoted to promoting its interests. At the same time, ideological or political issues without clearly defined social groups opposing each other cannot be defined as cleavages.Footnote ¹

Out of the four cleavages originally pointed out by Lipset and Rokkan, the class cleavage was the last to emerge but soon became the most important and most enduring one. It stemmed from the Industrial Revolution and gave rise at the corporate level to trade unions, and at the political and electoral levels, to socialist and social democratic parties that politicized the interest of the rising working class. While the other cleavages emerged only in certain contexts and not in others—according to specific cultural, socio-economic, or political conditions—the class cleavage spread across Europe and was politicized everywhere during the historical phases of democratization, enfranchisement, and development of mass politics (Lipset and Rokkan Reference Lipset, Rokkan, Lipset and Rokkan1967; Rokkan Reference Rokkan1970).

Given it was a so-called functional cleavage, with opposing social groups (working class vs. employers) based on ideas and interests and cutting across the territory of the respective country, the class cleavage historically played the role of a “homogenizing cleavage” in the process of nationalization of politics. Indeed, it created nonterritorial nationwide alignments with opposing socialist and social democratic parties representing the working class and with conservative and liberal parties advocating the threatened interests of the bourgeoisie (Caramani Reference Caramani2004).

As a fundamental pillar of the well-known “social cleavage model” (Lipset and Rokkan Reference Lipset, Rokkan, Lipset and Rokkan1967), the alignment between the working class and its reference parties became “frozen” in the 1920s, modeled the shape of Western European party systems for decades and contributed to their long-term stability (Rose and Urwin Reference Rose and Urwin1970; Bartolini and Mair Reference Bartolini and Mair2007; Oskarson Reference Oskarson and Thomassen2005). Once structured in Western European countries, this cleavage became the foundation of the widespread left-right dimension of conflict that crystallized everywhere in Western Europe as the main dimension of political opposition in each party system (Fuchs and Klingemann Reference Fuchs, Klingemann, Jennings and Van Deth1990; Mair Reference Mair, Dalton and Klingemann2007).

Since the 1980s, the great bulk of studies about the class cleavage turned towards a micro-level perspective focusing on class voting, namely the association between voters’ occupational class and vote choice. Although individual class voting is not the object of this study, it is important to underline some key findings of this literature that are deeply intertwined with the macro-level research about the socio-structural and organizational roots of left electoral mobilization. In this regard, since the 1980s the literature on class voting has observed a decline in the explanatory power of class differences on vote choice (Flanagan and Dalton Reference Flanagan and Dalton1984; Franklin, Mackie, and Valen Reference Franklin, Mackie and Valen1992; Nieuwbeerta and Ultee Reference Nieuwbeerta and Ultee1999; Dalton Reference Dalton, LeDuc, Niemi and Norris2002; Knutsen Reference Knutsen2018).Footnote ² However, scholars disagree about the leading process causing such dealignment between class and vote choice.

On the one hand, a “behavioral dealignment” emerges as a result of a “proactive change of the electorate’s preferences” (Goldberg Reference Goldberg2020, 86). A generalized increase in societal affluence and better working conditions lead post-materialist values and “new politics” issues to enter the political debate. Consequently, individuals are more and more mobilized by individual leaders or according to specific issues (i.e., environment, multiculturalism, European integration) cutting across traditional class loyalties (Inglehart Reference Inglehart, Dalton, Flanagan and Beck1984; Kriesi Reference Kriesi1998; Dalton Reference Dalton, LeDuc, Niemi and Norris2002; Hooghe, Marks and Wilson Reference Hooghe, Marks and Wilson2002; Garzia Reference Garzia2014). As a result of changing habits and preferences, class divisions have become blurred and unable to explain differences in voting behavior (Clark and Lipset Reference Clark and Lipset2001).

On the other hand, the decline in class voting is also the result of globalization and de-industrialization processes. The industrial working class of Western democracies has shrunk in size, thus becoming electorally irrelevant (Best Reference Best2011). In other words, a “structural dealignment” has taken place, according to which “the importance of a cleavage has weakened simply because of a reduction or even ‘extinction’ of a social group, and not because the linking issue or subject has lost effect on vote choice” (Goldberg Reference Goldberg2020, 70).

Beyond these two bottom-up perspectives, a top-down approach focusing on party strategies has also emerged. According to this strand of literature, the weakened link between social classes and reference political parties is not symptomatic of a dealignment of class. Rather, it is due to top-down processes in which political parties, particularly social democratic ones, have moderated their ideological orientation and reduced the emphasis on traditional economic left goals, thus favoring a substantial convergence with the mainstream right (Mair Reference Mair2008; Dalton Reference Dalton2013; Evans and Tilley Reference Evans and Tilley2012, Reference Evans and Tilley2017). Thus, left-wing parties have appealed to different social groups, like public sector employees and socio-cultural professionals (Przeworski and Sprague Reference Przeworski and Sprague1986; Kitschelt Reference Kitschelt1994; Gingrich and Häusermann Reference Gingrich and Häusermann2015; Benedetto, Hix, and Mastrorocco Reference Benedetto, Hix and Mastrorocco2020). However, in so doing, they risk alienating the support of their traditional working-class base (Karreth, Polk, and Allen Reference Karreth, Polk and Allen2013; Abou-Chadi and Wagner Reference Abou-Chadi and Wagner2019).Footnote ³

While the top-down approach has the merit of putting party strategies back in the discussion, the role of parties (and trade unions) as organizational agencies of the class cleavage is a systematically neglected aspect of the literature on class voting, which instead focuses mostly on the socio-structural element of Bartolini and Mair’s conceptualization (Reference Bartolini and Mair2007) introduced earlier. Indeed, the organizational element is properly recognized as an important aspect of the class cleavage in the macro-historical study by Bartolini (Reference Bartolini2000). He focuses on the socio-structural and the organizational elements of the class cleavage and finds a consistent and fairly stable link between class cleavage aspects and left electoral mobilization. Despite the presence of relevant national variations, he observes an overall robust and enduring association between the presence of a strong industrial working class, high membership rates in trade unions and left-wing parties, and electoral support for class bloc parties (communist, socialist, and social democratic parties).Footnote ⁴ However, the current validity of Bartolini’s empirical results should be put into question for two main reasons.

First, the results he gets are drawn from the “golden age” of class politics, where the working class was mainly industry-based, and class bloc parties and trade unions were strong mass organizations. By working on a different time frame (i.e., 1946-2018) characterized by working-class shrinking and transformation, trade unions and left parties organizational decline, and the previously discussed ideological shift of class bloc parties, will left electoral mobilization still be linked to the class cleavage’s socio-structural and organizational roots?Footnote ⁵

Second, Bartolini’s empirical analysis does not properly take into account the interactive dimension between class cleavage aspects and other important factors. For instance, as the socio-structural element is considered to be dependent upon the organizational one for the transformation of the social conflict into a proper cleavage (Bartolini Reference Bartolini2000, 16-25), does the interaction between two class cleavage elements positively affect left electoral mobilization? Moreover, as class is not the only source of identity and conflict within a society, does the presence of rooted cultural (i.e., ethnic, linguistic, religious) cleavages crosscutting class loyalties undermine the association between class cleavage roots and left electoral mobilization? Finally, as emphasized by the top-down approach of class voting literature, party strategies are expected to influence the relationship between the socio-structural element (i.e., the working class) and the support for class bloc parties. Therefore, another question to be addressed is whether the emphasis class bloc parties put on traditional economic left goals affects the association between the strength of the working class and the support for these parties. In the following sections, I try to take a step forward in the study of class cleavage roots and their electoral consequences by empirically addressing all the mentioned research questions.

Hypotheses

In the effort of tracing class cleavage roots behind left electoral mobilization, we need to start from the socio-structural and organizational elements of the class cleavage introduced in the previous section.Footnote ⁶

The socio-structural element of the class cleavage, its reference social group, is the working class. It is straightforward to hypothesize that a more favorable environment for the electoral success of the class left is a strong reference social group, namely a large and cohesive working class. While the latter can be generally considered as the group of people employed for wages,Footnote ⁷ the sectors considered relevant to forming the socio-structural element of the class cleavage can be a matter of debate. The traditional conceptualization and interpretation of the “owner-worker” cleavage (Lipset and Rokkan, Reference Lipset, Rokkan, Lipset and Rokkan1967) referred narrowly to the industrial working class. In particular, Bartolini (Reference Bartolini2000) argued that the strength of the working class could be mainly captured by two indicators, size and homogeneity. The former is the ratio between industrial workers and active population in a country and addresses the question of how large the putative social base of the class cleavage is. The latter, instead, refers to the ratio between the industrial working class and the entire working class and indicates to what extent the dependent labor force (i.e., the potential social base of the class cleavage) is industry-based rather than employed in agriculture or services. As for the size, the larger the industrial working class, the stronger the “social pressure of the group on its members toward attitudinal and behavioral conformity” (Bartolini Reference Bartolini2000, 145). As a result, working-class size “fosters socialist political recruitment and mobilization” (ibid., 146). To a similar extent, homogeneity is at least as important as size. Indeed, regardless of its overall size, Bartolini (Reference Bartolini2000, 152-153) argues that the greater potential for class bloc electoral mobilization lies in the industrial sector rather than in agriculture—whose proletariat is organizationally unstable, volatile, and unable to exploit collective action. Moreover, service workers were traditionally considered either “an essentially conservative element within modern society” (Goldthorpe Reference Goldthorpe, Giddens and Mackenzie1982, 180), or more likely to have postmaterialist or libertarian values compared to industrial workers (Inglehart Reference Inglehart1977; Knutsen Reference Knutsen2018).

More recently, however, the literature on class voting has tried to account for the increasing heterogeneity in the occupational structure, thus extending the working class beyond the industrial sector: scholars working on the “EGP class scheme” (Erikson, Goldthorpe, and Portocarero Reference Erikson, Goldthorpe and Portocarero1979) and those relying on the Oesch scheme (Oesch Reference Oesch2006) also consider farm laborers and service workers as among the working class.Footnote ⁸ This more encompassing interpretation of the working class leads us to consider, besides a measure for those employed in the industrial sector, a measure covering the total working class, thus including the dependent labor force in agriculture and services. Our first hypothesis is as a result:

The organizational element of the class cleavage involves both its corporate and partisan dimensions. The presence of strong organizations for the defense of the corporate and political interests of the working class is expected to be a crucial prerequisite for the electoral success of the class bloc. The underlying idea is that the more voters are encapsulated into the organization of trade unions, and even more, political parties representing their interests, the easier for such organizations to mobilize their putative constituency of voters (Bartolini Reference Bartolini2000).Footnote ⁹ Hence, the second hypothesis:

Besides these two main hypotheses, we also expect some interactive effects involving the two main class cleavage aspects and their relationship with time or other contextual factors.

To begin with, as the two aspects of the cleavage are deeply intertwined, we expect a positive interaction between them. On the one hand, the impact of a dense organizational encapsulation on the electoral support for the class bloc will be stronger the more powerful the reference social group is. This is because the organizational side of the cleavage is supposed to represent the armor of the otherwise politically defenseless working class: following this parallelism, the efficacy of the armor will also depend upon the strength of the body that wears it. On the other hand, as interaction effects are always symmetrical (Berry, Golder, and Milton Reference Berry, Golder and Milton2012), we also expect that the marginal effect of the socio-structural characteristics of the class cleavage on left electoral mobilization will be stronger the denser the organizational network of the cleavage is itself. Indeed, the positive electoral mobilization effects triggered by a sizeable and homogeneous working class (i.e., a strong social group) are likely to be further stimulated and multiplied by the presence of rooted corporate and partisan organizations that translate working-class interests from the societal to the political arena. Therefore:

Regarding the impact of class cleavage aspects across time, scholars have long debated about the resilience (Rose and Urwin Reference Rose and Urwin1970; Bartolini and Mair Reference Bartolini and Mair2007; Evans Reference Evans2000; Elff Reference Elff2007) vis-à-vis the decline of the class cleavage (Inglehart Reference Inglehart, Dalton, Flanagan and Beck1984; Franklin, Mackie, and Valen Reference Franklin, Mackie and Valen1992; Clark and Lipset Reference Clark and Lipset2001; Dalton Reference Dalton, LeDuc, Niemi and Norris2002; Knutsen Reference Knutsen2018; Goldberg Reference Goldberg2020). Yet most of this literature has addressed this topic through individual-level data to assess class voting decline. Conversely, I will test the effect of class cleavage roots on left electoral mobilization over time through aggregate-level data that, “while less informative, offer a necessary longer-term perspective” (Bartolini and Mair Reference Bartolini and Mair2007, 62). Consistently with the theory claiming class cleavage decline and dealignment in Western societies, we expect left electoral mobilization to be less linked to its class cleavage’s socio-structural and organizational roots as time goes by. As a result:

As far as other contextual factors are concerned, the presence of cultural cleavages is certainly expected to interact negatively with class cleavage aspects. Indeed, if the society is internally divided by ethnicity, language, or religion, this means that other allegiances also “crosscut” the working class, thus potentially undermining its ideological cohesion and sense of identity (see Rokkan Reference Rokkan1970; Bartolini and Mair Reference Bartolini and Mair2007; Lijphart Reference Lijphart1999; Nieuwbeerta and Ultee Reference Nieuwbeerta and Ultee1999). Therefore, cultural (i.e., ethnic, linguistic, or religious) heterogeneity can be understood as a factor undermining the development of a strong identity among the members of the working class. As a result, the positive marginal effect of social group strength and organizational density on class bloc electoral support is expected to decrease as cultural heterogeneity increases. Putting it differently, when other sources of membership (i.e., ethnicity, language, religion) threaten or challenge the socio-structural and organizational aspects of the class cleavage, the latter will have a lower impact on the electoral return of the class bloc. Therefore, our fifth hypothesis:

Moreover, we also believe that supply-side strategies play a role in the story (Dalton Reference Dalton2013; Jansen, Evans, and De Graaf Reference Jansen, Evans and De Graaf2013; Rennwald and Evans Reference Rennwald and Evans2014; Evans and Tilley Reference Evans and Tilley2012, Reference Evans and Tilley2017). Indeed, as class bloc parties are expected to represent the interests of their reference social group (i.e., the working class), the association between working-class size and homogeneity and support for class bloc parties will be closer the more class bloc parties are perceived as the legitimate delegates to represent working-class interests. This outcome is expected to occur as far as class bloc parties emphasize traditional economic left goals (e.g., welfare expansion, market regulation, controlled economy, equality, support for labor groups), thus continuously and consistently feeding and reinforcing working-class loyalty. Conversely, as far as such parties de-emphasize traditional economic left goals in favor of other non-class-related policies, they become increasingly perceived as outsiders and their linkage to the working class progressively fades (Sartori Reference Sartori1982, 152-153). At the same time, the impact of the organizational element (especially CPD) on left electoral mobilization is also expected to be influenced by the extent to which such organizations emphasize their reference to class interests. In other words, if class bloc parties are not perceived as credible in their attempt to represent working-class interests, their organizations, albeit strong, become as “empty vessels” (Katz and Kolodny Reference Katz, Kolodny, Katz and Mair1994) as far as left electoral mobilization is concerned. Therefore, we expect the following:

The Class Bloc: Composition, Electoral Support, and Programmatic Emphasis

The empirical analysis starts from the identification and operationalization of the dependent variable, the electoral mobilization of the class left. As we are interested in a systemic-level study, where the observation is not an individual party politicizing the class cleavage but instead the overall electoral strength of all parties politicizing it in a given time and space, we will focus on an aggregate measure, namely the class bloc electoral support.

The first task is the definition of the “class bloc” and the identification of parties belonging to it. In this regard, by relying on Bartolini and Mair (Reference Bartolini and Mair2007) and Bartolini (Reference Bartolini2000), we consider the historical communist, socialist, social democratic, and labor parties that originally emerged to mobilize the working class and to represent its interests in national political life. In other words, we include “those parties which are the historical product of the structuring of the working class movement” (Bartolini and Mair Reference Bartolini and Mair2007, 46), while parties of the “new politics” (Poguntke Reference Poguntke1987; Müller-Rommel Reference Müller-Rommel1989), which emphasize issues like environmentalism, feminism, or civil rights, have always been excluded.

From a methodological viewpoint, we have excluded parties that have never received 1% of the vote share in parliamentary elections. This choice was made to exclude minor parties whose potential inclusion in the class bloc was hard to assess with a sufficient degree of precision given the scarce information available.

As a result, for thirteen Western European countries (Austria, Belgium, Denmark, Finland, France, Germany, Ireland, Italy, Netherlands, Norway, Sweden, Switzerland, and United Kingdom) included in the original studies by Bartolini and Mair (Reference Bartolini and Mair2007, 285) and Bartolini (Reference Bartolini2000, 573–574) that cover the period up to the 1980s, we followed these authors’ criteria. However, as the class cleavage is not only a historical product but a dynamic concept, we have also carefully assessed the potential inclusion of all those parties that are direct successors of traditional working-class parties or new parties emphasizing traditional left issues. A qualitative assessment was needed to include class bloc parties in the aforementioned thirteen countries in recent years and in the remaining six countries (Cyprus, Greece, Iceland, Luxembourg, Portugal, and Spain) in the whole period. We have carefully considered all parties belonging to the communist, socialist, and social democratic party families in the ParlGov database (Döring and Manow Reference Döring and Manow2019) and in the communist and socialist party families in the Comparative Manifesto Project Database (CMP) (Volkens et al. Reference Volkens, Lehmann, Matthieß, Merz, Regel and Weßels2019). Then, by relying on the specific literature on these parties and party-related sources, we have excluded those parties that did not fit our substantive or methodological criteria.Footnote ¹⁰ Table A1 in the online appendix reports the list of ninety-eight class bloc parties resulting from this classification.

Once the class bloc is defined and the parties belonging to it are identified, the second task is to assess variation in the class bloc electoral support. The latter can be operationalized as the aggregate vote share collected by class bloc parties in a given country in a given parliamentary election (Lower House).

Overall, the average electoral support for class bloc parties is 38% in the 349 elections under study. As clearly displayed by the quadratic line in figure 1, the electoral support of class cleavage has proved to be substantially stable over time, with just a 3.5 percentage points variation over almost sixty-five years, namely from 1946 to 2010 (from the peak of 40.4% in the 1970s to 36.9% in the 2000s). Finally, a noticeable reduction is shown in the last decade (31.9% on average).

Figure 1 Electoral support for the class bloc over time in Western Europe (1946–2018)

Note: The observations in the figure represent the aggregate vote share collected by class bloc parties in a given parliamentary election (Lower House). Class bloc parties are communist, socialist, social democratic, or labor parties that have received 1% of the vote share in parliamentary elections at least once in their electoral history. The complete list of class bloc parties is reported in table A1 in the online appendix.

If we exclude Southern European countries where democracy comes back in the 1970s after the fall of the authoritarian regimes (Cyprus, Greece, Portugal, and Spain), and we focus only on the remaining fifteen countries where we have data points since the end of World War II, the electoral decline of the class bloc is more pronounced, with a range going from 40.2% in the 1960s to 27.6% in the 2010s. This means that to some extent the historical electoral decline of the class bloc in Nordic and Western European countries has been supplemented by the entry of electorally powerful class blocs in third-wave countries. At the same time, it highlights the importance of looking at national variations to gauge the phenomenon under study in greater detail.Footnote ¹¹

However, one may argue that the detected resilience of class bloc electoral support—albeit with a clear downward trend in the last decade—has little or nothing to do with the hold of the class cleavage. Conversely, one may hypothesize that, while the class cleavage has deeply declined in Western European societies in terms of social composition and organization, parties that once appealed to the working class are still able to maintain a fairly stable electoral support as they have reoriented their programmatic platform by de-emphasizing economic left issues and promoting a catchall appeal (Kirchheimer Reference Kirchheimer, La Palombara and Weiner1966; Mair Reference Mair2008; Dalton Reference Dalton2013; Evans and Tilley Reference Evans and Tilley2012, Reference Evans and Tilley2017). In other words, we could be in front of an issue of misplaced equivalence (Adcock and Collier Reference Adcock and Collier2001), as traditional left parties have maintained the same name and symbol but have changed their party platform compared to the 1960s or 1970s and no longer emphasize traditional class left goals. Testing empirically whether class bloc parties have shifted ideologically away from traditional economic left goals over time is, therefore, a crucial preliminary step to verify the validity of our operationalization with reference to the class cleavage. Consistently with recent comparative and longitudinal analyses (Jansen, Evans, and De Graaf Reference Jansen, Evans and De Graaf2013; Adam and Ftergioti Reference Adam and Ftergioti2019) our empirical tests based on data from the CMP between 1945 and 2018 (Volkens et al. Reference Volkens, Lehmann, Matthieß, Merz, Regel and Weßels2019) finds unequivocally that class bloc parties have not reduced their emphasis for traditional economic left goals over time (refer to table A2 and the related discussion in the online appendix). Therefore, the selected class bloc parties can be safely considered as the legitimate representatives of the working-class side of the class cleavage.

Data and Method

The operationalization of our main independent variables follows. Data about Industrial working-class size, Total working-class size, and Working-class homogeneity have been taken from Bartolini (Reference Bartolini2000) for earlier years (up to the 1970s), while for later ones the source is the International Labour Organization (ILO), supplemented by data from the Organization for Economic Cooperation and Development (OECD) in case of gaps in the ILO data.Footnote ¹² Following international standards and previous literature (e.g., Mainwaring and Zoco Reference Mainwaring and Zoco2007), we define industrial workers as those dependent laborers employed in mining, manufacturing, construction, and transport. Preliminary regression models, reported in the online appendix (table A4), show that it is precisely the size of the industrial working class, rather than that of the working class as a whole (including agriculture and service workers) that matter for left electoral mobilization. Consequently, we have excluded total working-class size from the following analyses and, given that industrial working-class size and working-class homogeneity are highly collinear (Pearson’s r = .796), we have combined the two variables expressed in standardized forms into the index of Social group strength.

The level of organizational density can be captured through the use of two indicators (Bartolini and Mair Reference Bartolini and Mair2007, 231–38; Bartolini Reference Bartolini2000, 262–63). The first refers to the corporate channel and is Trade union density (TUD), which is the ratio between union membership and the total dependent labor force of a country. TUD data have been collected from Visser (Reference Visser2016).Footnote ¹³ The second indicator instead refers to the partisan channel and is the ratio between class bloc parties’ membership and the total electorate (Class partisan density, CPD). As regards CPD, the source for the collection of data on class parties’ membership has been the MAPP Project Data Archive (Van Haute and Paulis Reference Van Haute and Paulis2016).Footnote ¹⁴ As in the case of socio-structural factors, also TUD and CPD are tested separately and then combined into a standardized index of Organizational density.

By looking at figures 2 and 3 we get a synthetic scheme of the temporal evolution and national variations of the socio-structural and organization aspects of the class cleavage. To begin with, consistently with the vast literature emphasizing working-class shrinking and left parties’ organizational decline (Dalton Reference Dalton, LeDuc, Niemi and Norris2002, Reference Dalton2013; Mair Reference Mair2008; Best Reference Best2011; Goldberg Reference Goldberg2020), our data show that all class-cleavage related variables decline over time.Footnote ¹⁵ This general picture is fairly consistent across countries, as displayed by figure 2, which contrasts the temporal evolution of the two standardized indices of social group strength and organizational density (both rescaled to a 0–100 range to facilitate the comparison). Moreover, by contrasting country averages, as in the scatterplot of figure 3, interesting insights emerge. Indeed, the association between the two class cleavage-related aspects is lower than one might expect (r = .215). This means that the development of dense organizational networks (i.e., strong trade unions and left parties) is not necessarily linked to the presence of a sizeable and industry-based working class. This is the case of Germany and Switzerland—where a strong social group goes hand in hand with a comparatively weak organizational density—but also of Cyprus and Iceland, displaying the opposite situation of relatively strong organizations in a context of a small and heterogeneous working class. Not surprisingly, Scandinavian countries like Sweden and Denmark as well as Austria show the strongest class cleavage roots, while Greece and Ireland fall at the bottom of the rank.Footnote ¹⁶

Figure 2 Temporal evolution of social group strength and organizational density (1946–2018)

Note: Social group strength and organizational density are synthetic indices combining variables expressed in standardized forms. The former combines industrial working-class size and working-class homogeneity. The latter combines class partisan density and trade union density. Both indices have been rescaled to a 0–100 range.

Figure 3 Social group strength and organizational density: country averages

The impact of socio-structural and organizational roots of the class cleavage on class bloc electoral support is investigated also by looking at interaction effects with other factors (H4, H5, and H6). Specifically, Time is operationalized as the number of years elapsed since 1945. The addition of a trend variable is also particularly suitable in time-series analysis, as it provides control to problems of spurious correlations (Roberts and Wibbels Reference Roberts and Wibbels1999). The level of Cultural heterogeneity is assessed through the Fractionalization index (Alesina et al. Reference Alesina, Devleeschauwer, Easterly, Kurlat and Wacziarg2003). The index ranges from 0 to 1 where 0 means perfect homogeneity (the whole population in a country has the same ethnicity, language, and religion), and 1 means perfect heterogeneity (there is a 100% probability that two randomly selected individuals within a population belong to different ethnic, linguistic, or religious groups). As Alesina et al. (Reference Alesina, Devleeschauwer, Easterly, Kurlat and Wacziarg2003) do not provide cross-temporal variation, we have collected data from Bartolini (Reference Bartolini2000) until the 1970s, and Patsiurko, Campbell, and Hall (Reference Patsiurko, Campbell and Hall2012) for the most recent period.Footnote ¹⁷ To measure Class bloc emphasis on traditional economic left goals we have selected the following items in the CMP (Volkens et al. Reference Volkens, Lehmann, Matthieß, Merz, Regel and Weßels2019): market regulation (per403), economic planning (per404), control of the economy (per412), Marxist analysis (per415), equality (per503), welfare state (per504), and labor groups (per701).Footnote ¹⁸ Then we have built an index that weighs, within each bloc, the individual party emphasis for the respective party’s electoral support.

The empirical analyses will also be integrated by some other control variables that may have effects on the dependent variable. To begin, we control for the level of class bloc “Organizational cohesion” (Bartolini Reference Bartolini2000), namely the number of parties included in the class bloc in a given country in a given election.Footnote ¹⁹ We will then control for systemic properties such as the overall level of ideological polarization in the country (through Dalton’s Polarization index (Reference Dalton2008)Footnote ²⁰ and the electoral system (through the natural log of the Average district magnitude, which is calculated by dividing the total number of seats to be allocated by the total number of districts).Footnote ²¹ Furthermore, we will also add a dichotomous variable for Third-wave democracies (Huntington Reference Huntington1991), namely Cyprus, Greece, Portugal, and Spain, where democracy came back only in the 1970s, and the class cleavage emerged in different structural conditions compared to the rest of Western Europe.

Figure 4 reports a synthetic scheme of all hypotheses, factors, measures, and expected effect on class bloc vote share, while table A3 in the online appendix reports the descriptive statistics of the dependent and (unlogged) independent variables.

Figure 4 Synthetic scheme of hypotheses, factors, measures, and expected effect on class bloc vote share

From a methodological viewpoint, we deal with pooled time-series cross-section data (Beck and Katz Reference Beck and Katz1995) with repeated observations over time (elections) on the same units (countries). In this context, problems of heteroscedasticity and autocorrelation may arise (Stimson Reference Stimson1985). Diagnostic tests such as an LR-test for panel-heteroskedasticity (p<.001) and a Wooldridge test of autocorrelation (p<.05) (Drukker Reference Drukker2003) confirmed such concerns. Moreover, we have performed a Hausman test to compare the results of fixed and random effects models. The result is that H0 (i.e., the difference in the coefficients is not systematic) is not rejected and hence we can use a random effects model. Moreover, given that some covariates in the models are almost or completely time-invariant (e.g., average district magnitude, the dummy for third-wave democracies), the inclusion of country-fixed effects is not recommendable (Beck and Katz Reference Beck and Katz2007; Mainwaring, Gervasoni, and España-Najera Reference Mainwaring, Gervasoni and España-Najera2017; Imai and Kim Reference Imai and Kim2019).

Hence, in the next section, the previously raised hypotheses will be tested through a model specification that is able to tackle such issues deriving from the data structure. We opted for a Prais-Winsten regression, namely a panel-corrected standard errors method (PCSE) with a first-order autoregressive parameter (AR1).Footnote ²²

Empirical Analysis

Table 1 presents the results of the empirical models. Model 1 displays the general plain model, while Models 2–8 test the previously hypothesized interaction effects.Footnote ²³ The general plain model tests H1 and H2, namely the hypothesized positive effect of, respectively, the socio-structural and the organization elements of the class cleavage on left electoral mobilization.Footnote ²⁴

Table 1 Determinants of class bloc vote share in Western Europe after 1945

Note: Prais-Winsten AR1 regressions; panel-corrected standard errors are reported. †p < .10; *p < .05, **p < .01, ***p < .001.

The general plain model (Model 1) shows that both class cleavage factors emerge as positive and significant predictors of left electoral mobilization. As a result, H1 and H2 are confirmed.Footnote ²⁵ By comparing the effects of social group strength and organizational density, the latter shows a comparatively larger impact on left electoral mobilization. Indeed, as organizational density increases by one percentage point, class bloc vote share increases by 0.14 points against 0.11 in the case of a one percentage point increase of social group strength.Footnote ²⁶

Table A5 in the online appendix offers some robustness checks with a replication of Model 1 in Table 1 across three different model specifications: a feasible generalized least squares (FGLS) regression (Parks Reference Parks1967) with a specification for panel heteroscedasticity and an autoregressive parameter (AR1); a panel-corrected standard errors regression (Beck and Katz Reference Beck and Katz1995) without the specification for autocorrelation; a generalized linear model (GLM) estimator with logit link function (Costalli and Ruggeri Reference Costalli and Ruggeri2019). Substantive results are consistent with those in table 1 across different specifications.Footnote ²⁷

So far, we have tested our first two hypotheses involving the linear effect of the two aspects of the class cleavage on the electoral success for the class bloc. We now turn to the analysis of the interactive models (H3–H6), reported in table 1 (Models 2–8).

Starting from H3, Model 2 shows that the interaction between social group strength and organizational density is statistically significant (at p<.05), as expected. This means that the marginal effect of organizational density on class bloc vote share increases as far as social group strength increases, and vice versa. As shown by the marginal plots reported in Figure 5, on the one side (right pane), the advantage of having a strong organizational network becomes tangible only at a certain level of industrial working-class size and homogeneity. In other words, with a meager and heterogeneous (i.e., not industry-based) working class, a powerful organization is not able to yield noticeable electoral returns. On the other side (left pane), the strength of the reference social group has an impact on the electoral support for the class bloc only if there is a certain level of organizational encapsulation.

Figure 5 Marginal effects on class bloc vote share of the interactions among the two aspects of the class cleavage

Regarding H5, Models 5 and 6 of table 1 yield different results. While confirming the hypothesized negative interaction between class cleavage aspects and cultural heterogeneity, only social group strength is influenced by cultural cleavages in a statistically significant way (the interaction term is significant at p<.01). More specifically, social group strength plays a significant role in the electoral success of the class bloc only when cultural heterogeneity is below a certain threshold, say 0.34 (80% of the observations fall below this threshold; see also the marginal plot in figure 6). Conversely, dense corporate and partisan organizational networks play a positive and significant role on left electoral mobilization regardless of the extent to which the society is ethnically, linguistically, or religiously divided.Footnote ²⁸

Figure 6 Marginal effect of social group strength on class bloc vote share at different levels of cultural heterogeneity

Turning to the interaction effect between the two class cleavage aspects and class bloc emphasis on traditional economic left goals (H6), Models 7 and 8 do not support our expectation. The organizational element of the class cleavage is shown to be unrelated to the extent that political parties appeal to their putative reference social group. In other words, organizations matter, regardless of the policy proposals they emphasize.Footnote ²⁹ The interaction between social group strength and class bloc emphasis on traditional economic left goals is positive and significant, but only at p < .10. As a result, the more class bloc parties appeal to their putative social group, the closer the linkage between the working class and left electoral mobilization. However, following Berry, Golder, and Milton (Reference Berry, Golder and Milton2012, 660-662), that kind of effect is of trivial magnitude and, therefore, not substantively significant. The correct interpretation is therefore that the effect of social group strength on class bloc electoral support depends only slightly upon the extent to which class bloc parties emphasize traditional economic left goals.Footnote ³⁰

Finally, the results shown in Models 3 and 4 are surprising as they are partially against the expectation formulated in H4. Instead of showing unequivocally the declined class cleavage roots behind left electoral mobilization in Western Europe, Models 3 and 4 highlight a fundamental difference between the two aspects of the class cleavage. Indeed, as displayed by the steep negative slope of the marginal effect plotted in figure 7, the association between organizational density and class bloc vote share has dramatically collapsed in recent years. On the contrary, in the case of social group strength (Model 3), the interaction with time is not significant, suggesting that the association between working-class features and class bloc vote share has not substantively declined in recent years.

Figure 7 Marginal effect of organizational density on class bloc vote share at different levels of time

As further robustness checks of H4, we have run separate regressions of the general model (Model 1 in table 1) for two time periods, with the cutoff point set in 1989 (see table A6 in the online appendix). The first period (1946–1989) shows that the two aspects of the class cleavage are significant predictors of class bloc electoral support (both at p<0.001). Conversely, in the second period (1990–2018), consistent with figure 7,Footnote ³¹ the impact of organizational density becomes not significant, while that of social group strength maintains a significant impact on left electoral mobilization (albeit only at p<0.05). As a result, Hp4 is only partially confirmed, and this finding sheds new light on the relationship between left electoral mobilization and its cleavage roots. In contrast to Bartolini’s findings (Reference Bartolini2000), the organizational density, once the most important predictor of left electoral mobilization, no longer plays a significant role in the story.Footnote ³²

In other words, in the last twenty-five years, the electoral support for class bloc parties has been completely detached from the organizational density of the corporate and partisan channels that were alleged to represent working-class interests. However, the historical link between the industrial working class and the electoral support for class bloc parties has persisted over time and can be still detected nowadays. Therefore, notwithstanding the scholarly emphasis on class cleavage decline, there are still socio-structural class cleavage roots behind left electoral mobilization, although such mobilization no longer goes through the corporate and partisan organizations of the class cleavage.