West European party systems are facing a period of change (Crewe and Denver 1985; Dalton 1988; Dalton et al. 1984; Daalder and Mair 1983; Mair 1984, 1989a,b; Wolinetz 1988). This change is observ able at two levels, elect oral and partisan. At the elect oral level, intra party volat il ity has progress ively accel er ated in the 1980s and

‘there is little evid ence that this flux is likely to abate’ (Mair, 1989b: 169). At the partisan level, a series of indic at ors show the accel er ated process of ‘decom pos i tion of estab lished party ties’ (Dalton, 1988). The decline of party iden ti fic a tion, of the number of party members and of the degree of partisan involve ment (Mair, 1984) all indic ate that the previ ous endur ing ties between the elect or ate and estab lished parties are progress ively fading away, thus enabling the emer gence of new parties and/or new agen cies for the aggreg a tion of demands (Mair, 1984, 1989a; Reider, 1989).