In recent decades, so-called universal welfare states have experienced considerable immigration from non-Western countries and, accordingly, rising levels of ethnic diversity. On that basis, scholars have debated how ethnic diversity affects public opinion in recipient societies. The debate is to a significant extent shaped by studies of American public opinion, where public opinion on some issues is widely considered 'racialized', i.e. in part based on attitudes toward racial outgroups.

The dissertation examines whether by the same token, political attitudes in universal welfare states can become 'ethnicized', i.e. in part based on attitudes toward ethnic outgroups. The existing literature has tended to focus on the issue of welfare, where the expectation is that ethnic diversity will diminish public support. I outline a theoretical framework which explains why political attitudes can be ethnicized, but also why it is more likely for some issues (such as European integration or crime) than others (such as welfare).

The dissertation includes four stand-alone articles illustrating the influence of group identities in political cognition. Compared to the existing literature, they suggest that ethnicization is at once more limited (in that it is unlikely for the most widely discussed issue, welfare) and more pervasive (in that it can arise from local contexts as well as from media). Ethnicization of attitudes is one way in which immigration can influence political life, even when the political agenda ostensibly revolves around something else.