The Culture War and Partisan Polarization: State Political Parties, 1960–2018

Abstract Partisan polarization on “culture war” issues has become a defining feature of contemporary American politics. This was not always the case; for the first two-thirds of the twentieth century, social issues such as abortion and LGBTQ rights played no role in politics. Where and when did the partisan divide begin? Did the initiative come from state or national parties? Was there a critical moment, or was position change incremental? We have constructed an original database of nearly 2,000 state party platforms from 1960 to 2018. These platforms allow us to trace position-taking on these issues and generate estimates of platform ideology. By the time national parties took positions, we show, they lagged state-level position-taking. Contrary to long-held assumptions, we show that state party system polarization did not occur around any critical moment but rather was incremental.