Presidents, Prime Ministers and Legislative Behaviour: The Conditional Effect of Presidential Legislative Powers on Party Unity

Abstract

Abstract This article proposes a novel theoretical framework to account for the combined effects of regime type and patterns of executive authority on legislative party unity. We argue that broad presidential legislative powers favour coordination between the president and legislative parties under pure presidentialism, whereas under semi-presidentialism, strong presidents increase the potential for intra-executive conflict, submitting parties to cross-cutting pressures. We expect higher levels of legislative authority to increase party unity under presidentialism but decrease under semi-presidentialism. Moreover, when presidents are endowed with limited legislative authority, semi-presidentialism produces higher levels of party unity than presidentialism, but for sufficiently high levels of legislative authority there should be no difference across regime types. Our analyses of 1,586 pooled observations for 72 democracies from all regions of the world using the V-Dem measure of party cohesion demonstrate that presidential legislative authority, in combination with regime type, is indeed a key predictor of party unity.