Issue Activation and the Limits of Partisan Absorption: Immigration and Vote Choice in the 2012, 2016, and 2020 U.S. Presidential Elections

When do issues aligned with partisanship nonetheless exert independent effects on vote choice? We argue that sustained presidential governance can "activate" a partisan-aligned issue, transforming it from a background component of party identity into a direct basis for electoral evaluation. Using American National Election Studies data from 2012, 2016, and 2020, we find that immigration attitudes did not independently predict presidential vote choice in 2012 or 2016 after accounting for partisanship. By 2020, following four years of intensive immigration governance, immigration attitudes had a significant independent effect. Mediation analyses provide suggestive evidence that immigration shifted from influencing votes mainly through partisan identity in 2016 to serving as a direct evaluative criterion in 2020, even as partisan sorting increased. Trade attitudes showed no similar pattern, indicating that issue activation may depend on governance that reinforces existing partisan alignments.