“Post-truth politics” has become a buzzword in academic and wider public debate since the Brexit referendum and the US Presidential elections in 2016. This project connects to the strand of literature in political theory that views post-truth politics predominantly as a transformation in political culture whereby the status and symbolic authority of the truth in politics is declining. The aim of this three-year project is to study the role of populist actors in the emergence of such a post-truth political culture in liberal democracies. The specific focus is on populist actors’ attacks on the credibility and legitimacy of mainstream quality media and, in particular, public-service media. By focusing on three country cases (Iceland, Germany, and Canada), the project makes an empirical as well as theoretical contribution to the growing literature on the detrimental impact of post-truth politics on liberal democracies. The project addresses this topic along three dimensions, specifically (1) the role of populist parties, (2) the role of social movements and other civil-society organizations, and (3) the experience of journalists as targets of verbal as well as physical attacks. The project will generate three comparative papers corresponding to the project’s three analytical dimensions.