Coattails and spillover-effects: Quasi-experimental evidence from concurrent executive and legislative elections

Concurrent elections are widely used to increase turnout. We theorize and show empirically how concurrency affects electoral outcomes. First, concurrency increases turnout and thereby the participation of peripheral voters. Second, in combined elections, one electoral arena affects the other. In our case of majoritarian executive elections concurrent to proportional representation (PR) legislative elections, the centripetal tendency of majoritarian elections colors off to the concurrent PR race. Third, concurrency also entails spillovers of the incumbency advantage of executive officeholders to the concurrent legislative race. Drawing on quasi-random variation in local election timing in Germany, we show that concurrency increases turnout as well as council votes for the incumbent mayor's party and centrist parties more generally, with slightly more pronounced gains for the political left. As a consequence, concurrent elections consolidate party systems and political power by leading to less fragmented municipal councils and more unified local governments.