Silly example I calculated for myself: right-populist parties that join Europe of the Nations sweep all former communist countries minus Poland at 60% of elected MEPs, while sister parties fail to get on the ballot everywhere else. That's 69 MEPs, or 9.2% tof a total 747. Now, assuming similar ratios in the all-EU list vote, and using the 2009 population projections, Europe of the Nations would deserve 8.3% of the vote, or 62 MEPs.

So, the possibility is there, though I submit it is a minor effect.

_{*Lunatic*, n.
One whose delusions are out of fashion.}