But what is particularly interesting is how infrequently these conflicts occur. As the authors write,
In almost 90 per cent of all MEP vote decisions in the fifth parliament [1999-2004], MEPs did not find themselves torn between the positions of their European and national parties, and so were free to vote with both parties' majorities.
Doesn't this seem like an awfully high figure? Particularly for the continent that was pretty much rife with internal warfare from the Renaissance until 1945? I'm really curious how this ends up working. One answer would be agenda control; the European parties manage to avoid taking on roll call votes that cross-pressure their members. But the EP has remarkably little agenda control. The bulk of their legislation is handed to them by the European Commission.
Another, I think more likely, answer is the organizing power of ideology. The left-right dimension in politics seems something close to universal across countries, at least from my limited reading on the subject. So a lefty in Romania will have a roughly similar set of views to a lefty in Denmark, and both will be able to join the Party of European Socialists with remarkably little internal dissent. Maybe this wouldn't work if you expanded the sphere somewhat more, but it is impressive how well it works considering the diversity of nations already in the EP.