ABSTRACT
One of the most basic contentions of political science is that the institutional ‘rules of the game’ have important consequences for the operations of political systems. Of these, none is more important than the role of electoral systems in shaping both political behaviour and political outcomes. For instance, majority-enhancing electoral rules, such as plurality or ‘first-past-the-post’ systems, are thought to be associated with the development of a few large, aggregative parties formed along a basic left–right political cleavage (Duverger 1954). By contrast, proportional representation (PR), by allowing the direct translation of different social and ideological cleavages through the party system, is usually seen as encouraging a multiplicity of parties and a greater diversity of views and minority representation (Lijphart 1984). Other electoral models, such as mixed-member systems, are sometimes claimed to be ‘the best of both worlds’ but are typically ‘semi-proportional’ in their partisan impacts (Shugart and Wattenberg 2001). The interaction of different electoral system models with parliamentary, presidential or semi-presidential government represents perhaps the most consequential institutional choice for any democracy.
