Differences Matter: Partisan Heterogeneity and Cooperation in the European Union

Abstract

Partisanship is a fundamental feature of democratic politics, but the effect of states’ partisan preferences on international cooperation remains poorly understood. This paper analyzes the relationship between partisan heterogeneity and cooperation in the European Union (EU). We argue that partisan heterogeneity in the Council of Ministers increases distributional conflict between EU member states and worsens commitment problems, thereby decreasing the depth of cooperation. We test the theory against data on financial contributions to EU structural funds and development aid. The data indicate that partisan heterogeneity reduces member states’ incentives to contribute to European cooperation. More generally, we provide a new perspective on the role of domestic politics in international cooperation and offer an explanation for dynamic fluctuations in international cooperation.