Decision Making in Political Systems: Veto Players in Presidentialism, Parliamentarism, Multicameralism and Multipartyism

The article compares different political systems with respect to one property: their capacity to produce policy change. I define the basic concept of the article, the ‘veto player’: veto players are individual or collective actors whose agreement (by majority rule for collective actors) is required for a change of the status quo. Two categories of veto players are identified in the article: institutional and partisan. Institutional veto players (president, chambers) exist in presidential systems while partisan veto players (parties) exist at least in parliamentary systems. Westminster systems, dominant party systems and single-party minority governments have only one veto player, while coalitions in parliamentary systems, presidential or federal systems have multiple veto players. The potential for policy change decreases with the number of veto players, the lack of congruence (dissimilarity of policy positions among veto players) and the cohesion (similarity of policy positions among the constituent units of each veto player) of these players. The veto player framework produces results different from existing theories in comparative politics, but congruent with existing empirical studies. In addition, it permits comparisons across different political and party systems. Finally, the veto player framework enables predictions about government instability (in parliamentary systems) or regime instability (in presidential systems); these predictions are supported by available evidence.