This article analyzes coalition formation within the European Parliament (E
P) under the cooperation procedure through the analysis of a random sample
of 100 roll call votes. The authors find that generally, coalitions form on
the basis of ideology, not nationality, although they are able to identify
some national groups that occasionally vote against the majority of their
party group. More interestingly, they find that the political initiative wi
thin the EP belongs to the Left and that the majorities required at differe
nt stages affect not only the outcomes of votes but also the coalitions tha
t will form. Finally, a slight variation is found in coalition building dep
ending on the subject matter. On the basis of these findings, the authors s
uggest an alternative interpretation of the conflicts between the Council a
nd EP based on an ideological conflict about more (EP) or less (Council) re
gulation, as opposed to more or less integration.