Veto Power

An actor has veto power if an outcome cannot be reached without his or her approval. An actor who has veto power can ensure that he or she is not made worse off than under the status quo. A veto player is an actor who has (ex post) veto power. We can distinguish between veto power as a negative power and positive powers such as agenda-setting power. Veto power is generally a weaker form of power than agenda-setting.

Veto power can have various sources. If an agreement requires unanimity, for example, every actor enjoys veto power. In some instances, specific actors have been granted veto power by law. For example, under the U.S. Constitution, the president has veto power in the legislative process, though it is qualified by the fact that Congress can override it by a two-thirds majority vote in both houses. Each of the permanent members of the U.N. Security Council has an (unqualified) veto power. In contrast to such de jure veto power, some actors enjoy de facto veto power even when they are not formally involved in a decision. For example, important social groups (e.g., trade unions) might exercise de facto veto power over pieces of legislation because parliamentarians rely on their support to stay in office.

An important distinction involves the question of when veto power can be wielded. Ex ante veto power, often called gatekeeping power, allows an actor to prevent any action from being taken. For example, it is more or less the case that the U.S. House of Representatives cannot pass any bill on an issue unless the House committee with appropriate jurisdiction has reported a bill to the floor. In deciding whether or not to use its veto power, the committee (or other actor with gatekeeping power) will compare the current policy (status quo) to the likely outcome of a new decision. Actors who expect the outcome of the discussion to be less beneficial to them than the status quo can exercise their gatekeeping power and preserve the status quo. In contrast, ex post veto power gives actors the opportunity to exercise a veto after the end of a decision-making process. Thus, an actor with ex post veto power can effectively choose between the status quo and the outcome of the new discussion. However, ex post veto power can sometimes be used in an offensive, and somewhat ex ante, fashion. For example, a president can threaten to veto legislation passed by Congress if it does not meet his or her stated demands: if this threat is credible, Congress is forced to choose between his or her preferred legislation (if Congress gives in to the threat) and the status quo (otherwise).

The effectiveness of any type of veto power depends on the preference configuration of the actors and the location of the status quo. If the status quo is the most preferred policy of the veto player, no policy change is possible even if all other actors involved in the decision would prefer a change in policy. Thus, veto power has a strong effect in this situation. In contrast, if the preferences of the actors are aligned and the veto player agrees with the other actors on the undesirability of the status quo he or she will not use his or her veto power. Hence, veto power would be inconsequential. Spatial voting models provide an analytical tool to compare the effect of veto power based on the preference configuration, the location of the status quo, and the distribution of veto power.

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