Abstract
By a two-dimensional voting body we mean the following: the body is elected in several regional voting districts by proportional system based on multi-party competition of national political parties. Then the members of the body exercise dual responsibility: responsibility following from the party membership and responsibility following from regional affiliation.
In this paper we formulate the following problem: 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 coordination of aggregated groups (European political parties or national representations). In the both cases the voting has an ideological dimension (elementary unit is a national party group), difference is only in dimension of aggregation.
Power indices methodology is used to evaluate voting power of national party groups, European political parties and national representations in the cases of partisan and national coordination of voting behaviour.