Political scientists have long classified systems of government as parliamentary or presidential, two-party or multiparty, and so on, but such distinctions often fail to provide useful insights. For example, how are we to compare the United States, a presidential bicameral regime with two weak parties, to Denmark, a parliamentary unicameral regime with many strong parties? "Veto Players" advances an innovative understanding of how governments are structured. The real distinctions between political systems, contends George Tsebelis, are to be found in the extent to which they afford political actors veto power over policy choices. Drawing richly on game theory, he develops a scheme by which governments can thus be classified. He shows why an increase in the number of "veto players", or an increase in their ideological distance from each other, increases policy stability, impeding significant departures from the status quo. Policy stability affects a series of other key characteristics of polities, argues the author. For example, it leads to high judicial and bureaucratic independence, as well as high government instability (in parliamentary systems). The propositions derived from th