Electoral System Effects on the Ideological Composition of Legislatures: Evidence from a Swiss Vote Advice Application

How electoral systems shape the composition of parliaments is one of the perennial research questions in political science. While effects on sociodemographic markers like gender or occupational background are fairly easy to trace and have often been studied, some of the most interesting political variables are much harder to gauge. Central among these is the ideological orientation of candidates. The present study argues that the Swiss case provides unique opportunities to shed light on the question whether and how electoral systems impact upon the ideological composition of legislatures. Not only is the Swiss cantonal level characterized by a variety of electoral systems and frequent reforms which can be exploited for studying electoral systems effects. Additionally, there are exceptional data potentials to inform research on this question. To study the ideological composition of candidates and legislators, we rely on data from the Swiss vote advice application Smartvote, which collects preferences of individual candidates that tend to participate in fairly high numbers. What is more, Smartvote often contains more than twice as many items as conventional vote advice applications, covers most cantonal elections and has consistently done so for well over a decade.