Replication Data for: Challenging the Challengers? Quasi-Experimental Evidence on the Impact of the Bündnis Sahra Wagenknecht on German Party Competition

Electoral systems with proportional rules are ultimately a zero-sum game, wherein the successful entry of a newly emerged party into the electoral arena inevitably results in electoral losses for some established parties. This article examines the effect of a populist challenger’s entry into party competition, analyzing whether it primarily mobilizes formerly abstaining voters, exacerbates the decline of mainstream parties, or attenuates the rise of other populist challenger parties. Leveraging County Council elections in five German states as a quasi-experiment, we exploit variation in the participation of the Bündnis Sahra Wagenknecht (BSW) across municipalities. Using covariate balancing propensity scores, we weight municipalities on key sociodemographic, economic, and political covariates, ensuring credible as-if randomization to estimate the average treatment effect of BSW participation on turnout and established party vote shares. Our findings reveal a significant reduction in vote shares for all established parties except the right-wing populist Alternative für Deutschland, with no evidence of increased voter mobilization due to BSW’s entry. The results have important implications for party competition dynamics and the functioning of representative democracy in the presence of multiple populist challengers.