Legislators' Voting Behavior with Two Principals and Party Cohesion

Abstract

This paper studies legislators’ voting behavior with two principals and explores a new way of aggregating their behavior with respect to party cohesion. In particular, it focuses on members of the European Parliament (EP) whose voting behavior is influenced by both the national party leadership and the European Political Group (EPG) leadership. In so doing, it addresses the question of developing an observationally equivalent measure of national party cohesion in the EP. Theoretically, two different voting circumstances for MEPs’ voting behavior are specified with respect to the cooperation and the conflict between a national party and an EPG. It is shown that depending on the circumstances, MEPs’ behavioral incentives work differently. As a consequence, MEPs’ voting records are generated conditioned by totally independent voting mechanism. In this regard, this paper develops a weighting method of measuring national party cohesion consistent with the independent roll call record generation processes. Results show that the new measurement produces valid scores of national party cohesion in accordance with our empirical expectations.