Populism, Parliamentary Influence, and Executive Power

Common definitions of populism rely on three elements. Populists claim to represent the will of the people, they position themselves as outsiders who challenge the establishment, and they aim for a restoration of popular sovereignty (for example, Mudde Reference Mudde2004). Some scholars emphasize that populists have a distinct approach to communicating with the public, where negativity, emotional appeals, exaggeration, and confrontational language play a central role (for example, Nai Reference Nai2021; Widmann Reference Widmann2021). Populists do not have a common programmatic direction but can be found on the left and right sides of the political spectrum (Stavrakakis et al. Reference Stavrakakis2017). On the left side, populists typically emphasize issues related to economic inequality and redistribution through taxes and public spending. Their agendas tend to focus on economic dimensions, often featuring anti-capitalist and anti-globalization views, finding a main enemy in financial institutions and financial elites. By contrast, right-wing populists often identify ethnic, cultural, and religious minorities as threats to a nation's identity. Consequently, their agendas usually emphasize anti-immigration appeals and demands for cultural homogeneity and integration (Vachudova Reference Vachudova2021).

When populists gain parliamentary representation, they can influence legislation, policy debates, and the formation and stability of coalitions. However, they lack the executive authority to implement their positions directly. Populists in the legislature have a small degree of agenda-setting power by bringing issues to the forefront that may have been ignored by mainstream parties. Parliamentary debates may become more emotional (for example, Valentim and Widmann Reference Valentim and Widmann2023) and more polarized (for example, Atzpodien Reference Atzpodien2022). In line with the theory of spatial political competition (Budge Reference Budge1994; Downs Reference Downs1957), the electoral success of populists may induce mainstream parties to change their policy positions – to regain lost vote shares (for example, Abou-Chadi and Stoetzer Reference Abou-Chadi and Stoetzer2020; Breyer Reference Breyer2023; Schumacher et al. Reference Schumacher2016), to adjust to changed voter preferences (for example, Adams et al. Reference Adams2004; Ezrow et al. Reference Ezrow2010; Klüver and Spoon Reference Klüver and Spoon2016), or to strategically respond to the behaviour and positions of the populists (for example, Adams and Somer-Topcu Reference Adams and Somer-Topcu2009; Williams Reference Williams2015). For example, the emergence of right-wing populist or radical parties may cause mainstream parties to adopt more restrictive positions on immigration (Abou-Chadi and Krause Reference Abou-Chadi and Krause2018; Chou et al. Reference Chou2021; Han Reference Han2015; Schumacher and van Kersbergen Reference Schumacher and van Kersbergen2016; Van Spanje Reference van Spanje2010) or to reposition themselves in matters of welfare policy (Krause and Giebler Reference Krause and Giebler2020). In some cases, mainstream parties may decide to simply ignore emerging populists; for instance, when populists have a small vote share and are not perceived as a threat (Meguid Reference Meguid2005).

The chances that mainstream parties adjust their policy positions are arguably much higher when populists gain executive power, especially when a populist takes over as the state leader. There are at least three elements of why the effects of populist state leaders v. populists in parliament on mainstream parties differ: executive power, agenda-setting power, and the threat of institutional deterioration. First, populist state leaders may implement their positions directly; for example, via presidential orders; through their right to initiate legislation; or by re-structuring, closing, or creating governmental agencies. Second, compared to parliamentary influence, state leaders have considerably more resources and opportunities to address the public and set the agenda. For instance, the media tends to devote more attention to the government – and especially the state leader – rather than the opposition (for example, Garz and Sörensen Reference Garz and Sörensen2021). Hence, while it may be an option for mainstream parties to ignore populists in parliament, the agenda-setting power of the state leader could invalidate this option when a populist takes over this office. Third, many populist state leaders act in an authoritarian fashion to preserve their power, which may involve the suppression of opposition and civil society actors, the exclusion of independent experts, the restriction of free media (Huber and Schimpf Reference Huber and Schimpf2017; Juon and Bochsler Reference Juon and Bochsler2020), and erosion of central bank independence (Gavin and Manger Reference Gavin and Manger2023). Consequently, the overall quality of democratic institutions and processes declines (for example, Bellodi, Morelli, and Vannoni Reference Bellodi, Morelli and Vannoni2024; Peffley and Rohrschneider Reference Peffley and Rohrschneider2024; Waldner and Lust Reference Waldner and Lust2018), while corruption and nepotism increase (Sasso and Morelli Reference Sasso and Morelli2021; Szeidl and Szucs Reference Szeidl and Szucs2021). While populists may also erode democratic institutions through parliamentary influence, the institutional deterioration under populist state leaders poses a particularly strong threat to democracy. Considering that mainstream parties usually value democracy, they face additional pressure to adapt under populist state leadership.

In summary, with populist state leaders, the pressure for mainstream parties to reposition themselves is arguably much higher when populists are merely represented in parliament, due to the state leader's executive power, agenda-setting power, and the threat of institutional deterioration. This pressure is likely highest in areas that are at the core of populists' agenda, including equality/welfare in the case of left-wing populists and multiculturalism in the case of right-wing populists. These areas could be decisive in the upcoming elections, due to the salience of related topics to the electorate when a populist is in power. Hence, repositioning themselves on issues related to equality/welfare and multiculturalism may be the key for mainstream parties to remain relevant in the media and win back voters. We discuss the options to adjust their positions below.

Strategic Responses to Populism and Implications for Party Systems

Understanding the system-wide impact of populist state leaders requires a discussion of the strategy options that individual mainstream parties have. They may decide to ignore the agenda of the populist (dismissive strategy), converge towards this agenda (accommodating strategy), or differentiate from it (adversarial strategy).Footnote ⁵ Collectively, these strategies could lead to a homogenization or differentiation of choices available to voters in a party system.Footnote ⁶ Party competition, inherently, is a dynamic process (Budge, Ezrow, and McDonald Reference Budge, Ezrow and McDonald2010; Laver and Sergenti Reference Laver and Sergenti2012), implying that parties may change their positions before a populist takes over as the state leader; for example, when populists gain vote shares in parliament. However, we limit the theoretical discussion to possible adjustments once a populist acts as the incumbent state leader to keep the argument simple and in line with our empirical design, and because adjustments of party positions to populists gaining strength prior to entering office have been previously discussed in the literature (for example, Krause and Giebler Reference Krause and Giebler2020; Schumacher and van Kersbergen Reference Schumacher and van Kersbergen2016).

Panel A of Fig. 1 illustrates the case where the mainstream parties of a country implement dismissive strategies to maximize their chances in the upcoming election, implying no change in positions and hence no change in the degree of diversity of choices they collectively provide. As argued above, this strategy is unlikely to be applied in practice due to the strong pressure that mainstream parties experience when a populist takes over as state leader.

Figure 1. Theoretical effects of populist state leaders on party positioning.

Notes: The figure refers to a fictional party system with an incumbent populist state leader, where three mainstream parties (a, b, and c) implement different strategies aimed at maximizing votes in the upcoming elections. The dots denote the location of parties' positions on a policy issue in a spectrum of hypothetical choices. A larger distance between two dots indicates a greater level of differentiation between parties. The arrows indicate adjustments in policy positions between the previous and the upcoming elections. The position of the incumbent populist state leader (and their party) is the one observed by the mainstream parties during the previous elections and assumed to be fixed for the sake of simplicity.

Panel B of Fig. 1 depicts a scenario where mainstream parties implement an accommodating strategy, resulting in homogenization of the party system. Accommodation is an often-used response in situations where right-wing parties gain parliamentary influence and could be a relevant strategy in our context. When a populist is the incumbent state leader, mainstream parties may attempt to win back votes by converging towards the positions that characterize the populist's agenda. If that strategy dominates among all parties participating in an election, their positions should, overall, become more similar, leading to a homogenization of choices available to voters.

Panels C and D of Fig. 1 illustrate scenarios in which mainstream parties use adversarial strategies to position themselves for the upcoming election. We argue that parties' incentives to use an adversarial strategy are particularly strong when the incumbent state leader is a populist. Once populists take executive responsibility, they usually face the dilemma that their anti-establishment views are not compatible with effective governance (Adams et al. Reference Adams2022). That is, populists may have to abandon (parts of) their rhetorical strategy, or they may fail to provide solutions to pressing issues. Either strategy comes at the risk of losing voter support. Given this dilemma, mainstream parties have strong incentives to work on ‘demystifying’ the populist leader by making broken promises salient, pointing out unresolved problems, and emphasizing the inadequacy of the populist's policy approach – all combined with their own proposals for alternative, better policy options.

The implementation of adversarial strategies can have different implications for the availability of choices in the party system. Panel C of Fig. 1 depicts the case where mainstream parties increase the distance from the populists while converging with each other. This scenario could be relevant if parties believe that the chances of having the populist voted out of office are best when they join forces; for example, because they believe that they reach a necessary majority only by combining their vote shares. In that case, the choices available to voters would be more homogenous.

However, adversarial strategies could also lead to greater diversification of choices (Fig. 1, Panel D). That is, mainstream parties may not only seek to distance themselves from the populist, but they may also choose a position that is sufficiently distinct from that of their mainstream competitors. This scenario could be particularly relevant for complex issues that offer plenty of space for differentiation, such as immigration. For instance, if the incumbent populist is in favour of closing the border to all refugees, the mainstream party (a) a may suggest welcoming all refugees if they apply for asylum while still being abroad, party (b) could propose to open the border for political refugees but not economic migrants, and party (c) may offer to prioritize highly educated migrants.

Finally, it is conceivable that a mix of accommodating and adversarial strategies leads to polarization of the party system (Fig. 1, Panel E). In that case, mainstream parties distance themselves from the incumbent populist while adopting positions at the extreme ends of the spectrum. This scenario does not necessarily imply that voters have more choices but that the choices are concentrated in two poles; that is, where the options available in a party system are presented in a binary manner (either/or, for/against).

Overall, the discussion shows that the effect of a populist state leader on party positions is theoretically ambiguous. It is conceivable that a combination of some or all of the possible strategies applies. For instance, some parties may decide to converge to the populist while others distance themselves; some parties may want to collaborate while others prefer to adopt unique positions. Hence, it is necessary to empirically investigate whether and in what situations any of the scenarios shown in Panels A to E dominate. Specifically, it is useful to evaluate whether a party system is more likely to become homogenous or differentiated under a populist leader. The reason is that the level of diversity of choices collectively provided by a party system has implications for the representation of citizens' preferences, political participation, and trust (Campbell and Heath Reference Campbell and Heath2021; Ezrow Reference Ezrow2007). For example, overly homogenous systems offer little diversity of policy alternatives, in which case there could be a disconnect between parties and voters. Highly polarized systems are not optimal either, as parties may have difficulties finding a consensus, or may not be able to work with each other because of a lack of agreement about fundamental issues. Normatively speaking, it is optimal if the parties collectively offer diverse policy choices (Benson Reference Benson2023). Collective decision-making may be more complicated in that case due to the difficulties of finding majorities and forming coalitions. Voters may also suffer from choice overload. However, those challenges are secondary, whereas representation and a diversity of choices are of primary importance. Hence, a party system that offers a variety of choices can be considered optimal from a normative perspective (Powell Reference Powell1982; Sartori Reference Sartori1976).

Panel F illustrates how position differences between parties can be empirically operationalized. For example, it is possible to calculate the absolute difference Y of position statements y between pairs of parties i and j (that is, Y _i,j = |y _i − y _j|). The mean difference over all pairs of mainstream parties n participating in an election would then yield a system-level measure of the dispersion of positions (Andrews and Money Reference Andrews and Money2009):

(1)$$\bar{Y} = \displaystyle{1 \over n}\mathop \sum \limits_{\,j = 1}^n \mathop \sum \limits_{i = 1}^n \vert {y_i-y_j} \vert $$

Low values of $\bar{Y}$ indicate a homogenous distribution of positions in the party system, whereas high values reflect a differentiated distribution.

Data

To evaluate the effects of populist state leaders on party positions, we compile a dyadic panel dataset that compares mainstream parties participating in the same election, with repeated observations from 215 national and presidential elections between 1989 and 2018 in 51 democracies around the world: see Table A1 in the Supplementary Information for a full list. Using party pairs as the unit of observation allows us to evaluate both the impact of populist state leaders on the party system at large (as described in Equation 1) and the distribution of positions between individual parties. The included countries and investigation period are determined by the availability of parties' election manifestos with content-analytical data in the Manifesto Project Database, as well as the availability of complementary data described below. Using observations on as many countries and years as possible gives us the best chance to obtain generalizable results, and it allows us to test for differences between political systems and countries' states of development.

Semantic Measures of Party Positions

The coding scheme of the Manifesto Project does not assess how parties propose to implement their positions or what their specific policy approach looks like. For instance, the annotations may indicate that two parties are in favour of expanding education, but one party proposes to strengthen universities while the other one prefers to hire more elementary school teachers. Similarly, there could be cases where the annotations suggest that two parties are in favour of multiculturalism but one party promises to foster the recruitment of high-skilled workers from abroad while the other party wants to legalize undocumented immigrants. Hence, the annotations in the Manifesto Project Database face limitations when evaluating parties' differentiation strategies (cp. Akkerman Reference Akkerman2015; Protsyk and Garaz Reference Protsyk and Garaz2011).

For that reason, we re-analyze the content-analytical data of the Manifesto Project Database by using automated text analysis. The basic idea is to compare the statements made by a party in a given category (for example, equality/welfare) with the statements of another party in the same category. If the content of their statements overlaps, both parties can be assumed to share similar ideas and policy approaches. By contrast, if there is little overlap between statements, the parties offer different views in that category. Automated text analysis has been widely used to compare political texts. For example, a growing literature on political media bias relies on analyses of textual similarities to show that a media outlet and a political party share the same ideology if they use similar language (for example, Garz and Rickardsson Reference Garz and Rickardsson2023; Gentzkow and Shapiro Reference Gentzkow and Shapiro2010; Martin and Yurukoglu Reference Martin and Yurukoglu2017).

We implement the comparison by modelling the semantic similarity of manifesto statements using Bidirectional Encoder Representations from Transformers (BERT), similar to the approach proposed by Ceron, Nikolaev, and Padó (Reference Ceron, Nikolaev and Padó2023). Transformer models tend to outperform previous approaches on most natural language processing tasks, such as text classification, named entity recognition, part-of-speech tagging, and multilingual analysis (Devlin et al. Reference Devlin2018; Licht Reference Licht2023). We use a multilingual version of Sentence-BERT designed to evaluate the semantic similarity of texts when different languages are involved. The model is trained in more than 100 languages and supports text comparison both within and across languages (Reimers and Gurevych Reference Reimers and Gurevych2020). The ability to make cross-language comparisons is important in our context, considering that parties in some countries compete in more than one language (for example, Belgium). In addition, the model was trained to catch the meaning of a statement independent of phrasing, which implies that our measure of differentiation of positions primarily captures differences in substance rather than rhetorical differences or different writing styles. The advantage of using a transformer model over other methods used for text comparison (for example, word2vec) is that context-specific meanings of words are retained. That is, the transformer model generates individual vectors of embeddings for the same word when used in different contexts (for example, ‘house key’ and ‘key of a song’).

We retain the full text of all statements (‘quasi-sentences’) falling in the policy categories under consideration (that is, equality/welfare and multiculturalism), as tagged by the coders of the Manifesto Project. These statements (225,291 in total) form a text corpus of 1,963,930 words. We use the multilingual Sentence-BERT to extract the word embeddings and create numerical representations of the statements, on which we compute the cosine distance for all possible combinations of statements between all pairs of mainstream parties participating in the same election.Footnote ¹⁰ For each policy category, we then compute the mean cosine distance between party pairs and rescale the resulting variables to vary between 0 and 1. Values closer to zero indicate that the statements made by a party in a policy category overlap with the statements made by another party in the same category, whereas values closer to 1 reflect little overlap.Footnote ¹¹

We verify the validity of the approach by qualitatively evaluating randomly selected manifesto pairs from those 19 countriesFootnote ¹² with languages spoken among the two co-authors using the method of close reading (for example, Grimmer and Stewart Reference Grimmer and Stewart2013). We confirm that the cosine distance based on the Sentence-BERT model facilitates an accurate comparison of semantic overlap both for individual pairs of statements and larger manifesto parts. For the sake of brevity, we illustrate the results of this exercise with English-language manifestos only.

Tables 1 and 2 compare random manifesto paragraphs with relatively similar and relatively different content, respectively. For example, Table 1 shows statements about equality and welfare by the Democratic and Republican parties from their manifestos before the 2004 United States elections. Both parties generically talk about the importance of educating children, yielding a relatively low value of the cosine distance (0.44) for these paragraphs.

Table 1. Examples of manifesto paragraphs with relatively similar content

Notes: The cosine distance is based on word embeddings extracted via a pre-trained S-BERT sentence transformer model. The measure is bound between 0 and 1. Larger values indicate low levels of overlap.

Table 2. Examples of manifesto paragraphs with relatively different content

Notes: The cosine distance is based on word embeddings extracted via a pre-trained S-BERT sentence transformer model. The measure is bound between 0 and 1. Larger values indicate low levels of overlap.

As an opposite example, Table 2 shows two paragraphs related to multiculturalism by the same parties in 2012. Here the Democratic Party talks about immigration, its benefits for the country, and the need for policy reform in that area. By contrast, the paragraph from the Republican Party manifesto discusses questions related to Indigenous Americans, thus addressing a completely different topic. Accordingly, the cosine distance between both paragraphs is relatively high (0.78). Tables 1 and 2 provide further examples from other countries and policy categories, all suggesting the same result: If two parties have similar proposals, the cosine distance takes low values, whereas it takes high values when two parties present different proposals.

Table A2 illustrates how the semantic measure of position differentiation differs from the traditional position measure. The table lists all statements in the welfare state category by the New Zealand National Party and Green Party of Aotearoa New Zealand in their 2011 manifestos. According to the traditional measure – which refers to the percentage of positive statements minus the percentage of negative statements – both parties would be assumed to have almost identical positions in that area as they are both in favour of expanding the welfare state. By contrast, with a value of 0.83 (that is, close to 1), the average cosine distance indicates that both parties are fairly differentiated in the matter. The reason is that the New Zealand National Party primarily talks about the pension system, whereas the Green Party of Aotearoa New Zealand discusses various aspects of the welfare state, including health, education, housing, and support of local communities.

As another example, Table A3 lists all statements in the multiculturalism category by Canada's New Democratic Party and the Conservative Party from their 2015 manifestos. The traditional measure again indicates very similar positions, whereas the average cosine distance (0.64) suggests a moderate to high level of semantic differentiation. Looking at the statements confirms that there is little overlap between the parties: while both of them pledge their support for Indigenous languages and communities, the Conservative Party – but not the New Democratic Party – talks about problems related to immigration (for example, honour killings, forced marriages) and requirements for Canadian citizenship.

Populist State Leaders

For each of the 215 elections in our dataset, we check whether the incumbent state leader appears in the database of populist leaders compiled by Funke, Schularick, and Trebesch (Reference Funke, Schularick and Trebesch2023). This database categorizes state leaders between 1900 and 2018 in 60 countries as right-wing populist, left-wing populist, or non-populist based on a systematic literature review of 770 sources. The definition applied to compile this database identifies state leaders as populist if they claim to be the sole representative of ‘the people’ in a fight against dishonest elites, similar to Mudde's (Reference Mudde2004) characterization. We prefer to use this database over other populism databases because the classification criteria are suitable for both presidential and parliamentary systems as well as advanced and emerging countries. Importantly, the data covers more countries and longer periods than alternative sources (for example, Hawkins et al. Reference Hawkins2019; Kyle and Meyer Reference Kyle and Meyer2020), which maximizes the number of observations in our analysis dataset.

Using this database, we identify a total of 11 populists acting as incumbent president or prime minister in 22 elections: Boyko Borisov, Recep Tayyip Erdoğan, Lech Kaczyński, Carlos Menem, Benjamin Netanyahu, Viktor Orbán (all right-wing populists), Robert Fico, Cristina Fernández de Kirchner, Evo Morales, Aléxis Tsípras, and Jacob Zuma (all left-wing populists): see Table 3 for details. We retrieve their party affiliation to match them with the manifesto data and create binary treatment variables that tag those elections where the incumbent state leader is a right- or left-wing populist.

Table 3. Populist leaders in the sample

Notes: The sample excludes those elections and incumbent populist leaders where annotated manifestos are not available.

Empirical Strategy

Estimating the effect of populist state leaders on mainstream parties' positions is challenging, due to confounding factors and reverse causality. For instance, the broader patterns in a nation's political and economic landscape as well as voter preferences may simultaneously influence the choice of its state leader and parties' strategies. Similarly, party positioning in earlier elections may affect the choice of the current state leader. For example, populists may emerge if mainstream parties fail to represent their citizens (Kriesi Reference Kriesi2014) or if mainstream parties collude and use public resources to collectively survive (Katz and Mair Reference Katz and Mair1995).

We tackle these challenges as follows. First, we address the issue of reverse causality by investigating the impact of the incumbent state leader on party manifestos. While the past behaviour of mainstream parties may affect the selection of the state leader, the selection of the incumbent cannot be influenced by party positioning in the future. Second, we estimate the effect of populist state leaders on positions in a panel model with two-way fixed effects. Including country fixed effects helps to account for the overall tendencies of countries to elect a populist state leader, as well as baseline differences in the degree of homogenization/differentiation of the party system (for example, due to the configuration of electoral rules; see Cox Reference Cox1990). Time fixed effects capture global trends in populism over time. Third, and most importantly, we use propensity score matching (Rosenbaum and Rubin Reference Rosenbaum and Rubin1983) to find ‘statistical twins’ for countries with an incumbent populist state leader.Footnote ¹³ For each treated party pair, we find one or more untreated party pair(s) with a similar propensity score based on observable factors related to populism; that is, economic conditions (GDP, inflation, and unemployment), the quality of institutions, and public sentiment towards populism (proxied by populists' parliamentary vote shares).

The aggregate parliamentary vote share of populist parties is a particularly powerful matching variable because it allows us to compare elections under similar public sentiment conditions towards populism, but where one election is treated with a populist incumbent state leader and the other is not. This approach is similar in spirit to Abou-Chadi and Krause's (Reference Abou-Chadi and Krause2018) approach, who use a regression-discontinuity design to compare parties that have similar vote shares but differ in their representation in parliament due to electoral thresholds. A regression-discontinuity design is not possible in our context though because the selection of the state leader is not always based on a quantifiable assignment rule but the result of negotiations between certain parties, which is why we rely on a matching approach.

We provide a detailed description of the matching procedure in the Supplementary Information. In short, we first use a probit model to estimate the impact of the political, economic, and institutional variables mentioned above on the likelihood of observing an incumbent populist state leader in a given election, yielding propensity scores for each treated and control observation. We then use kernel matching to compute weights that minimize the observed differences between treated and control groups.Footnote ¹⁴ As Table 4 shows, prior to matching, we observe significant differences in means of most variables between treated and control observations. After the matching, these differences disappear (Table 5), which suggests that the matching yields a dataset that is balanced on observables.

Table 4. Summary statistics (pre-matching)

Notes: Treated observations are those with a populist state leader, while untreated observations are those with a non-populist state leader.

Table 5. Differences between treated and untreated observations after matching

Notes: N = 2,083. Matching based on propensity scores.

We use the matched dataset to estimate the impact of incumbent populist state leaders on the distribution of positions of mainstream parties in a given policy category:Footnote ¹⁵

(2)$$Y_{i, j, e, c, t} = \alpha _1Pop_{e, c, t}^{left} + \alpha _2Pop_{e, c, t}^{right} + \alpha _3L_{i, j, e, c, t} + \theta _c + \vartheta _t + \varepsilon _{i, j, e, c, t}$$

where Y _i,j,e,c,t is the difference in positions between a pair of parties i and j participating in election e in country c and year t. Pop ^left and Pop ^right are binary treatment indicators. The coefficients α ₁ and α ₂ measure the average treatment effect of left- and right-wing incumbent populist state leaders, respectively, on position differences over treated party pairs. Considering that the treatment takes place at the election level (that is, all parties participating in an election face the same incumbent state leader), the treatment effects refer to the party system as a whole. That is, the coefficients α ₁ and α ₂ quantify the difference in the dispersion of positions between treated and untreated elections, which can be interpreted as changes in an election-level measure of dispersion similar to $\bar{Y}$ in Equation 1 in the theory section. A negative sign of α ₁ and α ₂ implies a more homogenous distribution of positions, whereas a positive sign indicates the opposite. The binary indicator L takes the value 1 for party pairs with a non-populist state leader, and 0 otherwise. θ _c and $\vartheta _t$ are country and year fixed effects.Footnote ¹⁶ We compute standard errors that are clustered by election – consistent with the level of treatment – to account for the correlation between party pairs participating in the same election (Cameron and Miller Reference Cameron and Miller2015).Footnote ¹⁷

With matched data, the treatment effects from Equation 1 capture reactions by mainstream parties to populist incumbent state leaders in addition to any changes in positions that may have been made prior to or independent of that, such as responses to populists gaining strength in parliament. For example, matching the aggregate parliamentary vote share of populist parties implies that we compare situations where mainstream parties have similar incentives to adjust their positions, but where some observations are treated and others are not.