Despite their potential importance, little is known about the nature and prevalence of party identification dynamics within American presidential campaigns. This study reviews existing research to propose three basic contrasting models. It then introduces multivariate state space methods that account for sampling error and survey design effects to evaluate each model’s relative support within daily national survey data of the 1984, 2000, 2004, and 2008 presidential campaigns. The results indicate that the balance of party identifiers had near-certain changes during three of the four campaigns, with campaign events often being associated with these changes. These findings suggest that polls and analyses that fail to allow for sudden shifts in party identifications will mask changes in public opinion. More generally, the findings demonstrate that campaigns shape party coalitions on Election Day, and possibly thereafter.

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