This paper studies a model of political parties as informative "brands" to voters. Voters across a large number of constituencies are assumed to be risk averse and incompletely informed about candidate ideal policies, and candidates are unable to commit to a declared policy platform. In this environment, parties can play a critical role by aggregating ideologically similar candidates and signaling their preferences to voters. This signaling is effective because party membership imposes costs, which screen out candidates whose preferences are not sufficiently close to the party's platform. We find that when party labels are very informative, the parties' platforms converge. When party labels are less informative, however, platforms diverge, because taking an extreme position allows a party to reduce the variance of its members' preferences. As parties become less able to impose costs on their members, or less able to screen out certain types of candidates, their platforms move further apart.

W e present a model of learning and policy choice across governments. Governments choose policies with known ideological positions but initially unknown valence benefits, possibly learning about those benefits between the model's two periods. There are two variants of the model; in one, governments only learn from their own experiences, whereas in the other they learn from one another's experiments. Based on similarities between these two versions, we illustrate that much accepted scholarly evidence of policy diffusion could simply have arisen through independent actions by governments that only learn from their own experiences. However, differences between the game-theoretic and decision-theoretic models point the way to future empirical tests that discern learning-based policy diffusion from independent policy adoptions.

We examine the relationship between parliamentary seats and cabinet posts in European governments between 1946 and 2001. Our speci¯cation improves on past studies in two respects. First, it derives and uses the voting weights of the underlying coalition formation games. This reduces the measurement error introduced when seat shares are used to proxy for voting weights. Second, the statistical model allows us to nest the predictions of di®er-ent formal theories of the distribution of posts. We¯nd that for non-formateur parties in the government, there is a linear relationship between their share of the voting weight in parliament and their share of cabinet posts. Additionally, the formateur party receives a substantial \bonus" relative to its voting weight. The latter¯nding is more consistent with proposal-based bargaining models of coalition formation, and less so with demand-bargaining models.

Organizations often distribute resources through weighted voting. We analyze this setting using a noncooperative bargaining game based on the Baron-Ferejohn (1989) model. Unlike analyses derived from cooperative game theory, we find that each voter's expected payoff is proportional to her voting weight. An exception occurs when many high-weight voters exist, as low-weight voters may expect disproportionately high payoffs due to proposal power. The model also predicts that, ex post, the coalition formateur (the party chosen to form a coalition) will receive a disproportionately high payoff. Using data from coalition governments from 1946 to 2001, we find strong evidence of such formateur effects.

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