The Logic of Contamination: District-Level Party Systems

Abstract

Even before mixed systems rose to the status they currently enjoy—the most fashionable set of electoral institutions—Maurice Duverger (1985, 72) discussed how these electoral rules are characterized by a spill-over effect: “Politically, this combination of the English system and PR exerts a pressure toward a two-party system as a result of the first vote, which influences citizens in how they cast their second vote.” Duverger envisioned a kind of interactive effect whereby the two-party competition that is typical of majoritarian races would spill over to the proportional tier. In both components of the election, the party system should approximate “bipolar” arrangements, in spite of the tendency of proportional representation to encourage the proliferation of parties.