Group formation, change and composition.

Voting by the public and parliamentary coalition formation are often separate processes in West European politics. Only in first-past-the-post systems like the UK is there a near-automatic link between voter choice and the formation of parliamentary majorities. However, in most proportional Systems with multi-party government, voters do usually know how the parties for which they are voting are likely to team up. Not only does this become an election issue in itself, the post-electoral coalition formation is transparent and widely understood, so any deceptions or unwise decisions can be subsequently sanctioned by the voters. In the case of the EP, however, the transnational party groups to which MEPs adhere once they have been elected under their national parties, are almost completely unfamiliar to the public and their composition is rarely debated at election time. The names of the transnational party federations are not, for example, included on ballot papers alongside national party labels. This gives national parties a wide margin for manoeuvre in their choice of an EP party group. On the other hand, parliamentary coalition formation in the EP is for far more limited purposes than in national political arenas. Transnational party groups are not formed to support a government, or to organise opposition, still less to prepare for the mobilisation of votes in future elections. They are, in the main, coalitions formed between national parties to use the powers - and opportunities for political articulation - offered by the EP. This can produce some surprising alignments, together with a generally more fluid pattern of majority formation than is common in national parliaments in Western Europe.

It might be supposed that a sufficient explanation for the composition of the party groups is that they simply bracket the national political parties of West Europe into their pre-existing political families -Christian Democrats, Conservatives, Communists, Greens, Liberals and Social Democrats - without changing any of the boundaries between these to allow for the fact that the EP and EU constitutes a different political System to any found at the national level. This view would predict what political scientists would call an exogenous party system, in which parties - and their relative strengths - are defmed outside the institutions they serve and without reference to the rules for exercising power there. In other words, once formed out of the families spirituelles, the party groups in the European Parliament would be expected to remain fairly constant in composition, apart from perturbations caused by changes in the membership of the Union itself, or major realignments in domestic politics of member states, and entries or exits of whole parties from national party Systems, the likes of which tend only occur once in every two or three generations in most West European countries. The exogenous character of the EP party system would also seem to be reinforced by the second-order nature of European elections. The tendency for voters only to vote on national criteria inhibits the entry to European elections of entirely new Euro-parties, organised solely for the purposes of offering the voters alternative EU policy programmes or visions of European integration, and it means that the groups in the EP will not rise and fall at the ballot box on account of their performance in the Parliament itself In terms of votes, the choice that a national party makes of an EP group is virtually cost-free, and it is only likely to be constrained by elite-level arguments about the party's position on European integration.

An alternative possibility is that the composition of the party groups is partially adjusted to the power structures of the European Union itself and its Parliament; that they are, in political science parlance, endogenous. The evidence would, in fact, seem to support two very interesting propositions,

• Until the mid - 1980s, the party system in the EP was predominantly shaped by exogenous factors. However, it has more recently shown signs of endogenous development. Before the Single Act and Maastricht Treaties, it was only some of the smaller party groups that came under pressure to adapt their composition to the specific institutional contexts of the Union and the internal rules of the EP itself. Since then, even the larger players have had to contemplate groupings that have caused some surprises in terms of domestic politics and ideological alignments. Simultaneous extension in the competence of the Union and the powers of its Parliament has compelled national parties to reconsider whether their MEPs really are well positioned to exercise significant influence in the EP. In the new institutional setting, the price of getting this wrong is loss of influence over a significant stage in the making of policies and laws that affect the domestic environment.
• On the other hand, the groups in the EP party system have come under different degrees of pressure to shift from an exogenous to a more endogenous pattern of development since 1986. While the PES still largely defines itself out of national parties from a single political family that has long existed outside the EU's own institutions (exogenous), the recent evolution of the other groups has often been governed by competitive forces and institutional rules specific to the EU and EP (endogenous). Even amongst these others, the analysis which follows will show that the motives and dynamics that govern group formation and composition in the EP vary across the three categories of large, medium and small players.