Centripetal and centrifugal incentives in mixed-member proportional systems

Abstract

How does competition for first (candidate) and second ballot (party-list) votes affect the strategic positioning of parties in mixed-member proportional systems? We study this question in a simulation study of multiparty competition in the two tiers. In the first step, we use data from elections for the German Bundestag to estimate individual vote function for each tier based on ideology, policy, and valence incentives. We then use these parameter estimates to calibrate a model in which parties compete for either first- or second-tier votes. Results suggest that parties may face a dilemma when adopting a positional strategy. When national parties and their candidates hold significantly different valences, large valence advantages generate centripetal incentives whereas smaller valences exert a centrifugal pull. Overall, centrifugal incentives dominate the German mixed-member system.