Political theorists have long argued that a well-functioning democracy requires a degree of mutual respect and willingness to talk across difficult political divides. Yet these normative standards for political dialogue are difficult to meet when the public is deeply divided. Numerous empirical studies have documented that electorates, especially in America, are polarized along partisan lines, and this manifests itself as animus towards opposing party members. We extend this work by examining the emergence of affective polarization along lines drawn not by partisan loyalties but instead by identification with opinion-based groups formed in the wake of Britain's 2016 referendum on European Union membership. We study this in a critical juncture in British politics and identify a similar degree of affective polarization, out-group prejudice, and other forms of animus around this novel, cross-partisan cleavage. We present evidence from a range of original surveys and experiments to demonstrate the scope and consequences of affective polarization of the British electorate after the Brexit vote using implicit, explicit and behavioural indicators. Our findings show that strong in-group identities have formed along Brexit-vote lines, which cut across traditional party lines. This suggest that affective polarization is not restricted to partisanship but can emerge across other significant political cleavages with broader implications for the study of in-group identities and democracy.
