Immigration, Political Ideologies, and the Polarization of American Politics

We provide causal evidence showing that migration increased the polarization of politicians campaigning for the House of Representatives between 1992 and 2016. Our polarization measures derive from ideology data based on 3 million campaign contributions. Our shift-share estimates hold over the medium-run, although they wane over time. These effects are strengthened should counties host similarly educated or more culturally distant migrants. Contributors’ race, employment status and occupations play important roles. Our results hold when focusing specifically upon refugees, where we exploit the spatial and temporal variation stemming from the opening of refugee resettlement centers for the sake of causal identification.