



In the second place, we find that universal suffrage and the concomitant enfranchisement of working-class voters were necessary but not sufficient conditions to propel social democracy to victory.

In the first place, we show that its success depended on the political inclusion of specific social strata, mainly, the industrial working class, which socialist parties defined as their natural constituency (Lipset and Rokkan Reference Lipset and Rokkan1967 Przeworski and Sprague Reference Przeworski and Sprague1986). Our empirical analysis leads us to make three claims – with the first two integrating the two main theoretical approaches advanced so far to explain the growth of electoral socialism. We complement this analysis with interwar aggregate data at the local level on industrial structure, unions and social-democratic vote, and with a survey on party vote conducted for the election of 1960. Matching that (quasi-)individual information with data on trade union density and on membership in free churches and the temperance movement, we determine the economic and organizational covariates of turnout and partisan vote since the introduction of universal suffrage in 1909 and until the abolition of the plural vote in local elections in 1919 – a decade of fundamental electoral growth for Swedish social democrats. Collected by the electoral administration of Sweden, the data include the number of registered and eligible voters, whether they voted or not, and the party they voted for at a high level of disaggregation: by both local district and income segments – most of them defined by Kr. Here, we start to remedy this problem by relying on unique, highly granular data on Swedish local elections conducted between 19. Although the electoral rise and consolidation of social democracy has been the object of several path-breaking studies, their empirical validation has been marred by the fact that researchers have had to rely on aggregate electoral and social data for the period that preceded the systematic use of surveys.
