The Mainstreaming of Populist Rhetoric and Public Support for International Solidarity

How does the diffusion of populist rhetoric among populist and non-populist politicians affect public support for multilateral and bilateral foreign aid? Extant research shows that populist elite communication can reduce public support for international solidarity and trust in international organisations. However, framing effects are generally moderated by citizens’ evaluation of the source of the message. Indeed, recent work suggests that the effect of populist party cues remains limited to citizens who already hold favourable views of populists (Bayram & Thomson, 2022). However, in response to the electoral gains of populist parties, mainstream parties increasingly adopt populist frames and populist policy positions, leading to a “mainstreaming” of populist rhetoric. We argue that the use of populist frames and the adoption of populist positions by mainstream parties also affect citizens who are usually not responsive to cues from populist parties. In particular, we theorise that individuals who support mainstream parties might be affected by populist frames if they are voiced by mainstream political actors. Thus, populist discourse may undermine broader public support for multilateral international solidarity. We test this argument in the area of international health policy using a novel survey experiment embedded in a cross-national public opinion survey to be fielded in five European countries in late 2025. Specifically, the experiment varies the source – no source, right-wing populist party, centre-right mainstream party, and centre-left mainstream party – of a negative populist frame. Our study contributes to research on the effect of populism on public support for international solidarity and particularly to the effect of the diffusion and “normalisation” of populist rhetoric among mainstream parties. Finally, by investigating the relative importance of frames and party cues in the area of international solidarity, our study contributes to the long-standing debate on whether the message or the messenger matters more in shaping citizens’ opinions.