Like in the last Parliament, Europarties in the 7th Parliament are increasingly cohesive along Europarty lines rather than national lines. The big increases in cohesiveness were on budget and civil liberties, and deceases in environment and agriculture. The general trend is towards increased cohesion along ideological, Europarty lines, meaning that it's more important for voters to know which Europarty their candidates will sit in when they're electing them.
"In the current European Parliament, MEPs vote primarily along transnational political lines rather than along national lines, as in EP6. Proof of this is the fact that cohesion rates of the four largest European political groups (EPP, S&D, ALDE, and G/EFA) are invariably higher than the cohesion scores of member states’ delegations of MEPs. The only policy area where this does not hold is on agriculture: here, the European political groups are significantly less cohesive than on other policy issues and some national parties (particularly the French and the Scandinavians) vote independently of their group colleagues."
The big surprise is that, despite the big gains in the 2009 elections and the collapse of the S&D vote, the centre-right EPP is less successful in terms of being on the winning sides of votes than in the last Parliament. Likewise, the S&D group is marginally more successful. How did this happen? The answer is that ALDE, the liberal group, is aligning itself more with the S&D group, particularly when it comes to the budget and civil liberties - important areas, given the increased power of the EP in the justice and home affairs and budget areas of policy. Perhaps the centre-left are the overall/marginal "winners" of the Lisbon-era powers of the European Parliament (at least in the first 6 months)? What is known is that the Liberals' kingmaker position is stronger than ever, since with fewer EPP-S&D coalitions, the position of ALDE in forming coalitions with either party usually decides an issue. So this Parliament is general centre-left on civil liberties and the budget, but centre-right on internal market and industry.
The ECR, though I never expected them to be very successful, have turned out to have had a disappointing first 6 months. Despite saying that they will vote with the EPP when they have common interests, it doesn't seem as if the party has been able to form many coalitions with the EPP (or should that be vice-versa?). It should be noted that the ECR has fallen behind the Greens on size since the start of Parliament. The ECR are one of the least successful parties, just ahead of the far-left United Left and the Europe of Freedom and Democracy Group (the latter trials as the least successful and cohesive group).
But the question is, will the resilience of the centre-left continue to be as successful over the next six months or over the rest of the Parliament's mandate? The ECR and EPP may grow closer together as time passes and the wounds of the Tory-EPP split are put behind them. With the Tories in a coalition government in the UK (a strange ECR-ALDE coalition in EP terms), and a voice in the Council, the ECR may draw closer to the EPP and general Council line, encouraging more centre-right coalitions. On the other hand, if the centre-left continue to build stronger links between them, perhaps come election time there could be more common campaigning (perhaps even coalition campaigns for the Commission presidency?)? (Of course, that's pure speculation - the Europarties have to decide on how common their own campaigns can be first...)