George Tsebelis
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George Tsebelis is a Professor of Political Science at the University of Michigan. Tsebelis developed the theory of veto players, set out in his best known work, Veto Players: How Political Institutions Work (2002).
The ‘veto players’ concept is an old one, dating back at least 2000 years. Tsebelis synthesises and formalises it. A ‘veto player’ is an individual or collective actor who has to agree for the legislative status quo to change. Tsebelis argues that having many veto players makes significant policy changes difficult or impossible. Tsebelis also predicts that systems with a high number of veto players will pass few significant laws and will tend to high deficits (as the veto players need to be bought off). Tsebelis considers two types of veto players: institutional (those officially named somewhere, such as the President, Congress and Senate) and partisan (those whose veto arises from the system but is not one of the rules of the system, such as political parties). Some of these veto players, moreover, can present ‘take it or leave it’ proposals to the other veto players. Tsebelis calls these ‘agenda setters’.
According to Tsebelis, among feasible outcomes (that is, the shared winset of outcomes which meet each veto player’s requirement of being superior to the status quo), agenda setters pick the outcome that they like most. Tsebelis predicts that when few outcomes are feasible, agenda setters will have a small role; where none at all are possible (that is, there is no ‘core’ where all winsets overlap), agenda setters are irrelevant.