Behavioral researchers disagree sharply about how voters decide. These debates can be traced to various factors, including measurement problems inherent in survey research and the reciprocal relationships among the various independent variables that affect the vote choice. Here we focus on the impact of party identification on the vote. In subsequent chapters, we will show the relation of this issue to our analyses of party strategies. Behaviorists are similarly divided about the interrelationships among voting behavior, considerations arising from economic conditions, group attachments rooted in class and religion, and retrospective evaluations of incumbent performance.

The impact of party identification on voting behavior is a central feature of the “Michigan model” of voting (Campbell et al. 1960), in which the vote choice is conceptualized as the outcome of long-term forces – such as group loyalties and citizens' basic value orientations and partisan predispositions – and short-term factors, including candidate images, campaign issues, and economic conditions. According to this model, partisanship represents a long-term, affective, psychological identification with one's preferred party that is nonetheless distinct from voting preference, so that voters may vote for a candidate of one party while expressing loyalty to another party. Because the Michigan model posits that partisanship is an affective orientation – one that typically grows out of early socialization experiences – it does not necessarily represent some cognitive or “rational” decision process (see Jennings and Niemi 1981; Jennings and Markus 1984). Indeed, voters need not even be aware that partisanship affects their vote choices.