WHY PARTY SYSTEMS DIFFER
As we have seen, three different approaches--sociological, institutional, and competitive--have been utilized in the analysis of parties and party systems. The question of why party systems differed from one regime to another was one of the main areas of research in which the sociological and the institutional approaches provided very different answers. While the early institutionalists had seen electoral systems as the cause of different party systems, the sociological approach emphasized the centrality of divisions within society, and especially class divisions. As Lipset wrote in 1960:
More than anything else the party struggle is a conflict among classes, and the most impressive single fact about political party support is that in virtually every economically developed country the lower-income groups vote mainly for parties of the left, while the higher-income groups vote mainly for parties of the right. 1
As with all long-standing academic debates, though, the grounds of the controversy between the two approaches have shifted over the years. Thirty years ago the distinction between the two was relatively clear cut. Today many of the arguments originally made by the 'sociologists' are accepted by the 'institutionalists', and vice versa; where they differ is in the weight they attach to the different factors that determine the character of a particular party system. But a useful starting-point for our discussion is the sociological approach's emphasis on class; having explained this we can then turn to the distinctive features of the institutional approach.