Why have some territories performed better than others in the fight against COVID-19? This paper uses a novel dataset on excess mortality, trust and political polarization for 165 European regions to explore the role of social and political divisions in the remarkable regional differences in excess mortality during the first wave of the COVID-19 pandemic. First, we investigate whether regions characterized by a low social and political trust witnessed a higher excess mortality. Second, we argue that it is not only levels, but also polarization in trust among citizens - in particular, between government supporters and non-supporters - that matters for understanding why people in some regions have adopted more pro-healthy behaviour. Third, we explore the partisan make-up of regional parliaments and the relationship between political division - or what we refer to as 'uncooperative politics'. We hypothesize that the ideological positioning - in particular those that lean more populist - and ideological polarization among political parties is also linked to higher mortality. Accounting for a host of potential confounders, we find robust support that regions with lower levels of both social and political trust are associated with higher excess mortality, along with citizen polarization in institutional trust in some models. On the ideological make-up of regional parliaments, we find that, ceteris paribus, those that lean more 'tan' on the 'GAL-TAN' spectrum yielded higher excess mortality. Moreover, although we find limited evidence of elite polarization driving excess deaths on the left-right or GAL-TAN spectrums, partisan differences on the attitudes towards the European Union demonstrated significantly higher deaths, which we argue proxies for (anti)populism. Overall, we find that both lower citizen-level trust and populist elite-level ideological characteristics of regional parliaments are associated with higher excess mortality in European regions during the first wave of the pandemic.