Policy preferences, unity, and floor dissent in the European parliament

To what extent do individual members of the European Parliament (MEPs) have policy and ideological incentives to vote against their European Political Groups (EPGs) and national party delegations (NPDs), and how often they act on these by voting against the party line? Documenting over-time variations in incentives to dissent in floor votes using five waves of surveys of MEPs, covering the years 1994-2019, this article shows that while these have generally decreased over time, they remain substantial. Further, by combining individual floor voting records on legislation and individual MEP survey responses for the 2004-2009 EP, the article shows that while individual MEP preferences significantly influence the decision to dissent from the EPG line in floor votes, this is not the case for voting against their NPD, lending support to the argument that the primary principal for MEPs is their national party, not their EPG.