Strategic voting in large elections under proportional representation : Why vote for center parties ? ∗

Most of the countries in the democratic world use proportional representation to allocate seats in parliaments. There are typically more than two serious parties in those countries. Consequently, the two-party competition models do not help us much to understand the political economy of those countries. When there are more than two parties, it is no longer rational for voters to vote for the party they prefer. For instance, if one’s preferred party has no chance of being part of the future government, it may be utility maximizing to vote for another party and help it join the government. Consequently, a complete picture of proportional representation requires to take account of strategic behaviour both by parties and by voters. Parties are strategic in their choice of the proposed platform, as well as in their choice of which other parties they will form a coalition with in case they have their say in the forming of the winning government. Voters are strategic at the voting stage, and their choice of which party to vote for will