Political scientists know a lot about the opinion dynamics of the electorate as a whole, yet relatively little is known about the dynamics of mass parties. Much interesting distinct variation between the parties in the electorate is covered up through aggregation. This dissertation seeks to provide a better understanding of the American political system by incorporating measures of partisan opinion liberalism into distinct theories and models of macro politics. The dissertation project is based on measures of partisan policy mood, which gauge the demand for more or less liberal policy relative to the status quo for Democrats, Republicans, and independents in the electorate from 1951 through 2012. In the first empirical chapter I discuss the collection of these data and the process of creating annual estimates of policy mood for Democrats, Republicans, and independents in the electorate. I also provide an in-depth analysis of the over-time differences between the symbolic and operational ideologies for these three groups. There are clear distinctions between the symbolic and operational ideologies of Republicans and independents in the electorate, but remarkable consistency between these two conceptions of ideology for Democrats. The second empirical chapter applies the thermostatic model of opinion change to Democrats and Republicans in the electorate. The theory predicts similar opinion dynamics for Democrats and Republicans over time. While the findings support the prediction of parallel publics, the mechanism through which Democrats and Republicans respond to change differs; Democrats are responsive to changes in public policy, whereas Republicans are responsive to party control of government. Importantly, it does not appear as though policy significantly contributes to mass party polarization. I wrap up this chapter with a discussion on how the perceptions of policy held by Democrats and Republicans in the electorate can lead to the inference of mass party polarization even when the preferences of both sets of partisans are congruent and stable. The third empirical chapter focuses on representation. I develop a micro theory of partisan representation based on a member of Congress' electoral calculus to develop macro level expectations about policy responsiveness to partisan opinion. The findings indicate that policy is responsive to the opinion of the majority party's mass partisans, while independents and mass partisans of the out-party do not see their preferences translated into public policy. The finding contradicts research on representation of the mass electorate, but adds to the growing literature on the representation of sub-aggregate groups and representational inequality in the electorate.