Social Bases of Partisanship
Cleavage Structures and Intersectional Bases

Despite the growing significance of partisanship in the US, research on its social roots has been relatively stagnant since the late 1990s. We identify two distinct ways in which partisan identities can be rooted in social divisions: cleavage structures—capturing the depth and alignment of political cleavages—and intersectional structures—highlighting the political relevance of unique combinations of group memberships. We develop analytical tools to distinguish these forms empirically, which entails a (1) decomposition approach to measure both the depth and alignment of cleavages and (2) a model that overcomes the sparsity problem in analyzing the partisanship of a large number of intersectional categories. Analyzing the General Social Survey from 1977 to 2022, we find that the depth of individual cleavages—especially race and religion—has increased over time. At the same time, however, their alignment has weakened, producing growing crosspressures rather consistent pressure towards polarization. Furthermore, political identities are increasingly shaped at the intersection of social divisions. Our findings underscore the growing complexity of the social roots of partisanship in the US and call for a shift from examining single social divisions in isolation to analyzing the alignment of cleavages and intersections.