The era of the First World War constituted the defining moment of most contemporary European party systems. The most widespread and enduring aspect of this transformation from preindustrial to industrial cleavage structures was the gradual eclipse of centrist (liberal or agrarian) parties by socialist, social-democratic, and/or communist parties on the left. That this did not occur in the United States has often been regarded as the defining feature of the American party system. Others have suggested, somewhat to the contrary, that the Democratic party served as the functional equivalent of European social democracy such that there was nothing particularly exceptional about the development of the American party system.

What was the character of the left party in America during the first half of the twentieth century? Writers portray the Democratic party prior to the 1930s as an organization periodically drawn and quartered by the demands of its disparate constituents – northerners and southerners, farmers and urban laborers, immigrants and natives, wets and drys, progressives and reactionaries. According to this view, the realignment of 1896 heralded not so much the arrival of a new ideological age as the revival of an older Jacksonian framework. “[F]irmly rooted in negativism, clinging to outdated ideals of states' rights, retrenchment, and limited government,” one historian has written, “the Democratic party seemed a ramshackle, almost irrelevant array.” There was, in short, no single Democratic ideology but rather a great profusion of outlooks and interests.