National and ideological influence in the European Parliament

In this paper we address the following question: Taking as decisional units national chapters of European political parties, is there a difference between a priori voting power of national groups in the case of "national" coordination of voting and in the case of "partisan" coordination of voting? By coordination of voting we mean two step process: in the first step there is an internal voting in the groups of units (national or partisan), in the second step there is a voting of aggregated groups (European political parties or national representations) in the EP. In both cases the voting has an ideological dimension (elementary unit is a party group), difference is only in dimension of aggregation (European parties versus national representations). Power indices methodology is used to evaluate voting power of national party groups in the cases of partisan and national coordination of voting behaviour.