A Longitudinal Comparison of the Effects of Election Outcomes on System Legitimacy in the United Kingdom and United States

ABSTRACT Using three‐wave panel data from the United Kingdom ( N = 604) and the United States ( N = 512), we examined changes in system‐legitimization across the 2024 electoral cycle and whether trajectories differed for electoral winners and losers. In both countries, system‐legitimization increased after the election, suggesting that elections function as legitimacy‐relevant events once outcomes become known. Winner–loser dynamics qualified these patterns. In both countries, electoral winners showed clear post‐election increases in system legitimization. Among losers, responses depended on how political alignment was operationalized. In the United Kingdom, right‐leaning losers increased in system legitimization when defined by ideology, but Conservative Party supporters showed no substantive post‐election change. In the United States, left‐leaning losers showed little ideological change overall, whereas Democratic Party supporters exhibited a short‐term decline that was not sustained 1 month later. These findings suggest that elections shape system attitudes, but loser responses are contingent on political context and how electoral alignment is defined.