Abstract Partisan vitriol has become a defining feature of American politics, evident in survey responses and social media discourse. Conventional wisdom holds that these expressions reflect deeply rooted hostility. Yet they may also function as social signals, reinforcing loyalty and conformity within partisan groups. In this view, animosity is less about entrenched ideological divisions and more about fostering cohesion among co-partisans. We test this proposition in two settings. First, using the 2012 American National Election Studies, which recorded interviewer partisanship, we exploit within-interviewer variation to examine whether respondents adjusted their reported hostility depending on the partisan identity of their interviewer. Respondents expressed significantly more animosity when interviewed by a co-partisan and less when facing an opposing-partisan interviewer. Second, in an online experiment with 1,510 participants, we find that revealing a partner’s partisan alignment—when it matched the participant’s—encouraged more frequent out-group attacks and in-group promotion. These behaviours were strongly shaped by social norms: participants were substantially more likely to attack when their partner had done so in the previous round. Together, these findings suggest that partisan hostility is contingent on immediate social context, not solely on deeply held animus.
Ahn et al. (Wed,) studied this question.