Increasing number of studies is focusing attention to constitutional analysis of European Union institutions and distribution of intra-institutional and inter-institutional influence in the European Union decision making. Most of the studies are related to distribution of voting power in the EU Council of Ministers as reflecting the influence of member states (or, more precisely, member states governments). Significantly less attention is paid to the analysis of European Parliament (EP). 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 the both cases the voting has an ideological dimension (elementary unit is a party), difference is only in dimension of aggregation. Power indices methodology is used to evaluate voting power of national party groups in the cases of partisan and national coordination of voting behaviour.
a priori voting power European Parliament European political parties power indices Shapley-Shubik power index