This article presents a model of individuals' party identification that contrasts with previous models. Past models, with the few recent exceptions noted, assume a hierarchical relationship either from identification to other aspects of political behavior, such as the perception and evaluation of issues and candidates, or from these behaviors to party identifications. The model discussed here places party within a dynamic concept of the electoral process and tests several hypotheses about factors producing changes in identifications. The first factor, consistent with the spatial-type issue voting models, estimates the effects of the relative proximity of each party to the individual's own policy preferences. Second, we examine the effect of the actual voting decision on subsequent identifications, with the expectation that if votes differ from previous identifications, there is a resulting shift in partisanship. Finally, we examine the hypothesis that identifications become less susceptible to change as people age and accumulate political experience. When combined with other research, the results indicate a model of the electoral process in which party identifications are both influenced by circumstances specific to each election and influence other behaviors. This nonrecursive model has a number of implications for the development and evolution of individual and aggregate partisanship. These implications are discussed at the end of the article.

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CENTRAL question in the study of voting behavior is the question of /~ voter rationality. If voters make rational candidate selections, then 1-1 elections may serve as a control device to insure responsive public officials. Empirical research on voter rationality, however, reaches several different conclusions. Some studies2 find that voters fail to meet standards of rationality while others find most voters capable of rational vote choice.3 Underlying these research differences (other than a focus on different elections), are different perceptions of the type of behavior necessary to be considered rational. Some analyStS4 set high standards to determine whether or not a voter is rational. These proponents of synoptic rationality5 require a voter to be interested in politics, well informed on the issues, have clear guiding principles on which to base the vote decision, and rationally (a means-ends calculus) select the best candidate in terms of these guiding principles. Under this conception of rationality, a rational vote maximizes the desired output (the voter's utility) in terms of the voter's preferences while using all possible information. In most cases these analysts find that voters lack the cognitive abilities to meet this standard. Other students of electoral behavior argue that the investment of effort required by synoptic rationality may not, in fact, be rational If the costs involved in making a synoptic decision exceed the difference in benefits between the top two alternatives (candidates), then expending the time and resources necessary to make a synoptic decision would be a poor investment.

The assumption that individual preferences, or attitudes, are fixed and exogenously determined is central to many studies of political and economic institutions, such as markets and elections. We present a Bayesian model of adaptive preferences and empirical evidence consistent with that model to argue that preferences are not always exogenous and fixed. The changing relationships between partisanship and preferences on civil rights issues between 1956 and 1964 and on the Vietnam War issue between 1968 and 1972 coincide with significant changes in the major parties' positions on these issues, suggesting that preferences are endogenous to the electoral process. We conclude with a discussion of the positive and normative implications of endogenous preferences.