Four studies tested the hypothesis that psychological essentialism underlies political conservatism. Study 1 (n = 263) finds correlational evidence that essentialist thinking about the U.S. is correlated with support for three conservative ideologies (RWA, SDO, nationalism) and conservative policies regarding religion, taxes, the environment and immigration. Experiments show that prompting participants to think about the essence of the U.S. increases support for RWA and nationalism, but not SDO. Study 2 (n = 164) compares an essential to a non-essential framing of the U.S., while Study 3 (n = 150) compares essential framings of the U.S. to another concept (music). Parallel mediation analyses show that support for RWA and nationalism mediates the relationship between essentialism and support for conservative policy positions. Study 4 (n = 174) directly replicates Study 2 and goes further to test mediators, showing that perceptions of intergroup threat mediate the effect of an essential U.S. framing on RWA, while national identification mediates the effect on nationalism. We discuss how the different ways liberals and conservative Americans conceive their nation impacts political polarization. Data and materials are publicly available at (https://osf.io/srvxk/?view_only=3222ba5c750d4362b68b25ea80195d67)