In Partisan Nation, Paul Pierson and I argue that the particular characteristics of contemporary polarization in the United States are quite different from those experienced in earlier polarized periods in American political history. Particularly important has been the nationalization of mediating institutions, including state political parties, organized interests, and the media. This unprecedented configuration, in which polarized parties operate within a nationalized polity, generates acute challenges – ones that the American constitutional system was intended to prevent, and that it is poorly equipped to manage.
I have extended this line of argument in a recent article in Political Science Quarterly, "Donald Trump's Contributions to the Study of American Political Institutions" (October 2025; https://doi.org/10.1093/psquar/qqaf090)