Electoral institutions and legislative behaviour:explaining voting defection in the European parliament

Despite a sophisticated understanding of the impact of electoral institutions on macrolevel political behavior, little is known about the relationship between these institutions and microlevel legislative behavior. This article reviews existing claims about this relationship and develops a model for predicting how electoral institutions affect the relationship between parliamentarians and their party principals in the context of the European Parliament. The European Parliament is an ideal laboratory for investigating these effects, because in each European Union member state, different institutions are used to elect Members of European Parliament (MEPs). The results of this model, tested on four hundred thousand individual MEP vote decisions, show that candidate-centered electoral systems (such as open-list proportional representation or single-transferable-vote systems) and decentralized candidate-selection rules produce parliamentarians independent from their party principals. By contrast, party-centered electoral systems (such as closed-list proportional representation systems) and centralized candidate-selection rules produce parliamentarians beholden to the parties that fight elections and choose candidates: in the case of the European Parliament, the national parties.