A Model of Party Entry in Parliamentary Systems with Proportional Representation

Abstract

Spatial models with a party entry decision largely fall into one of two classes. The first of these preserves the Downsian assumptions that candidates are office-seeking and can announce policy positions anywhere in the policy space. A distinct class of models features what are now known as “citizen-candidates” who combine policy and office-seeking incentives, and who cannot credibly commit to implementing any policy other than their own ‘ideal point’ as a platform in electoral campaigns. The following paper develops a game theoretic model of party entry which employs mechanisms from each of these classes of analyses, but departs from both bodies of literature in studying party entry in Parliamentary regimes with Proportional Representation. Preliminary analysis of Subgame Perfect Nash Equilibrium suggests that, when parties are exclusively concerned with policy, party entry should be somewhat more likely when status quo parties are well-dispersed around the median voter’s ideal point than when they are both fairly centrist. However, as candidates’ office-seeking incentives begin to outpace their policy-seeking incentives, the relationship between status quo dispersion and entry becomes more complicated, and depends crucially on the ideal point of the entering candidate.