Parliamentary behaviour with two principals: preferences, parties, and voting in the European parliament

The European Parliament has be? come one of the most powerful insti? tutions in the European Union. Mem? bers of the European Parliament (MEPs) can now enact legislation, amend the European Union budget, veto the nominee for the European Union Commission President, and censure the Commission. But, we know little about what determines MEPs' voting behavior. Do they vote according to their personal policy preferences? Do the EP parties force MEPs to toe the party line? And, when national party and EP party preferences conflict, which way do MEPs respond?to the principals who control their election (the national parties) or the principals who control their influence in the EP (the EP par? ties)? The results reported here show that national party policies are the strongest predictors of voting behav? ior in the EP