Partisans Underestimate and are Influenced by In-and-Out-Party Dynamic Norms

Norms within the American political landscape are continually evolving. Framing norms as dynamic (changing over time) rather than static (fixed in the present) can encourage individuals to adopt counter-normative behaviors and attitudes. We investigated whether dynamic norm interventions reduce ideological polarization (divergence in policy attitudes between groups) and affective polarization (hostility toward opposing parties). In a pilot study (N = 50), we identified credible dynamic bipartisan norms (e.g., increasing bipartisan support for poverty assistance). In Study 1 (N = 389), Democrats and Republicans underestimated in-party and out-party support for these norms and misperceived trends, believing Republican support had declined when it had actually grown. In Study 2 (N = 1,187), exposure to dynamic bipartisan norms reduced ideological polarization but did not significantly reduce affective polarization, suggesting that shifting policy attitudes does not necessarily foster cross-party goodwill. Understanding these distinctions may inform interventions to bridge ideological divides.