A Socialist Threat? Electoral Competition, Interparty Coordination, and the Success of Social Democratic Candidates in Majoritarian Electoral Systems

The emergence of new parties and their impact on party systems has met considerable interest of political scientists. While many scholars have argued that increasing electoral competition affects policy positioning of established parties, they have largely neglected how the latter adopt their electoral strategies in majoritarian and proportional representation systems in response to new competitors. In this article, I demonstrate that established parties form electoral alliances to marginalize new parties in majoritarian electoral systems. Thereby, parties considerably influence the competitiveness of elections as well as the disproportionality of electoral outcomes by forging electoral alliances. To support my argument, I engage in the debate on the rise of social democratic parties ("Socialist Threat"), cooperation between non-socialist parties, and their link to the introduction of proportional representation, democratization, and welfare state development in early 20th century Europe. I use newly collected district data for all elections with runoffs in the German Reich between 1890 and 1912 to investigate the effect of social democratic candidates entering the second round on the alliance behavior of non-socialist parties. To obtain convincing causal estimates, I employ a regression discontinuity design by taking the first round vote share difference between the second non-socialist and the socialist candidate in order to measure the closeness with which the left candidate entered the runoff. In addition, I use multiple measures of electoral alliances to test the robustness of my results. The paper contributes to the literature on major social and political reforms at the turn to the 20th century as well as the debate on electoral competition, party positions, and their impact on public policies.