BY Shane Reynolds & Kévin Saudé (UL): Do voters become more affectively polarised when the party they support is on the losing side of a referendum? Affective Polarization (AP) refers to the difference between how much a voter likes a party (in-group favouritism) and the amount of dislike expressed towards the other parties (out-group derogation). The polarizing outcome of the United Kingdom’s decision to leave the European Union following a non-binding referendum has been in full display since 2016. Is the Brexit case idiosyncratic or does Affective Polarization responds more generally to referendum outcomes? We know that AP tends to increase during divisive and competitive electoral campaigns for parliamentary seats, and that post-election coalition agreement appeases party supporters. Hence, we should expect voters on the losing side of referendum to be – for some time at least – more affectively polarized. To test these arguments, we employ data from the Comparative Study of Electoral Systems (CSES) and hand-coded data on referendum outcomes between 1990-2021 which assembles system and party-level data on 28 referendums. The results will contribute to our knowledge of the causes of Affective Polarization so pervasive in Europe in recent years.