Chapter 2 described state-to-state differences in ideological and partisan identifications. With reasonable precision, that chapter identified which state electorates are most liberal and which are most conservative, as well as which state electorates are most Democratic and which are most Republican. Still to be answered, however, is why these state differences in mass preferences exist. The question is, Where do state-to-state differences in ideology or partisanship come from? Why, for instance, is Indiana more Republican than Missouri? Or for instance, why is Oklahoma more conservative than New York?

To some degree, state differences in political preferences follow simply from the states’ group compositions. Each state electorate is a unique composite of political groupings, and these help to determine the state's political views. For instance, if a state electorate is composed primarily of the kinds of people who lean in the liberal direction, we would expect the state as a whole to tilt in the liberal direction. But collective sentiment can be more than the sum of views of the represented groups. A second potential source of state attitudes is state residence itself. It could be that from exposure to the predominant political culture of their state, citizens are influenced to hold political views they otherwise would not. For instance, if a state electorate is composed of groups that typically lean in the liberal direction, the state electorate could still tilt conservative due to a (perhaps intangible) conservative political culture in the state.

Political scientists often assume that political attitudes are shaped by the local political culture or the commonly shared and reinforced political values within the local community.