The normative permissiveness of political partyism

Political party identity has become one of the strongest social divides within many Western societies. This paper employs experiments to measure discrimination along different dimensions of social identity, and replicates previous findings showing the strongest discrimination against out-groups occurs in the political party domain. Moreover, we explore a possible explanation for this phenomenon based on social norms. We measure the social appropriateness of discrimination along each identity dimension. The ranking of dimensions by discrimination against out-groups reflects the extent to which such behaviour is normatively permissible, with the weakest anti-discrimination norms on the political party dimension. Results are qualitatively similar in two European countries. We argue that, while strong norms sanctioning discrimination on other dimensions have developed historically, no such process has taken place concerning party affiliation, bringing partisan identity to the fore and helping polarisation flourish.