This paper analyzes the properties of runoff electoral systems when voters are strategic. A model of three-candidate runoff elections is presented, and two new features are included: the risk of upset victory in the second round is endogenous, and many types of runoff systems are considered. Three main results emerge. First, runoff elections produce equilibria in which only two candidates receive a positive fraction of the votes. Second, a sincere voting equilibrium does not always exist. Finally, runoff systems with a threshold below 50 percent produce an Ortega effect that may lead to the systematic victory of the Condorcet loser. (JEL C72, D72)

The majority runoff system is widely used around the world, yet our understanding of its properties and of voters' behavior is limited. In this paper, we fully characterize the set of strictly perfect voting equilibria in large three-candidate majority runoff elections. Considering all possible distributions of preference orderings and intensities, we prove that only two types of equilibria can exist. First, there are always equilibria in which only two candidates receive votes. Second, there may exist an equilibrium in which three candidates receive votes. Its characteristics challenge common beliefs: (i) neither sincere voting by all voters nor pushover tactics (i.e., supporters of the front-runner voting for a less preferred candidate so as to influence who will face the front-runner in the second round) are supported in equilibrium, and (ii) the winner does not necessarily have democratic legitimacy since the Condorcet winner may not even participate in the second round.

This paper both theoretically and experimentally studies the properties of plurality and approval voting when the majority is divided as a result of information imperfections. The minority backs a third alternative, which the majority views as strictly inferior. The majority thus faces two problems: aggregating information and coordinating to defeat the minority candidate. Two types of equilibria coexist under plurality: either voters aggregate information, but this requires splitting their votes, or they coordinate but cannot aggregate information. With approval voting, expected welfare is strictly higher, because some voters multiple vote to achieve both goals at once. In the laboratory, we observe both types of equilibrium under plurality. Which one is selected depends on the size of the minority. Approval voting vastly outperforms plurality. Finally, subject behavior suggests the need to study asymmetric equilibria.

This paper both theoretically and experimentally studies the properties of plurality and approval voting when the majority is divided as a result of information imperfections. The minority backs a third alternative, which the majority views as strictly inferior. The majority thus faces two problems: aggregating information and coordinating to defeat the minority candidate. Two types of equilibria coexist under plurality: either voters aggregate information, but this requires splitting their votes, or they coordinate but cannot aggregate information. With approval voting, expected welfare is strictly higher, because some voters multiple vote to achieve both goals at once. In the laboratory, we observe both types of equilibrium under plurality. Which one is selected depends on the size of the minority. Approval voting vastly outperforms plurality. Finally, subject behavior suggests the need to study asymmetric equilibria.

We study unanimous decision making under incomplete information. We argue that unanimous decision rules are not all equivalent. We show that majority rules with veto power are (i) Pareto superior to commonly used unanimous rules and (ii) ex ante efficient in a broad class of situations. We thank the coeditor, Jesse Shapiro, and five anonymous referees. We also thank participants of the

Why are U.S. congressmen reluctant to support gun control regulations, despite the fact that most Americans are in favor of them? We argue that re-election motives can lead politicians to take a pro-gun stance against the interests of an apathetic majority of the electorate, but in line with the interests of an intense minority. We develop a model of gun control choices in which incumbent politicians are both office and policy motivated, and voters differ in the direction and intensity of their preferences. We derive conditions under which politicians support gun control early in their terms, but oppose them when they approach re-election. We test the predictions of the model by analyzing votes on gun-related legislation in the U.S. Senate, in which one third of the members are up for re-election every two years. We find that senators are more likely to vote pro gun when they are close to facing re-election, a result which holds comparing both across and within legislators. Only Democratic senators "flip flop'' on gun control, and only if the group of pro-gun voters in their constituency is of intermediate size.

The rational-voter model is often criticized on the grounds that two of its central predictions (the paradox of voting and Duverger's Law) are at odds with reality. Recent theoretical advances suggest that these empirically unsound predictions might be an artifact of an (arguably unrealistic) assumption: the absence of aggregate uncertainty about the distribution of preferences in the electorate. In this paper, we propose direct empirical evidence of the effect of aggregate uncertainty in multicandidate elections. Adopting a theory-based experimental approach, we explore whether aggregate uncertainty indeed favors the emergence of non-Duverger's law equilibria in plurality elections. Our experimental results support the main theoretical predictions: sincere voting is a predominant strategy under aggregate uncertainty, whereas without aggregate uncertainty, voters massively coordinate their votes behind one candidate, who wins almost surely.

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