Explaining group membership in the European Parliament: the British Conservatives and the Movement for European Reform

Abstract: This article examines the decisions behind group membership in the European Parliament (EP) using a rational-choice institutionalist framework. Following the goals ascribed to them by Strøm (1990) in other settings, national parties should join the largest group that matches their socioeconomic preferences. Yet, whilst explanations taking national parties as the basic unit of analysis might sometimes suffice, we argue that it is often necessary to consider the influence of individual parliamentarians and existing EP groups. The scope open to these various actors to pursue their interests determines the attractiveness of the various options available to a national party. We illustrate our conceptual framework by reference to the attempt by the British Conservative Party to leave the European People's Party-European Democrats (EPP-ED) group, an effort ending in the formation of an extra-parliamentary federation, the Movement for European Reform.