Academic research focuses on political communication of populist radical right parties and on their discourses about the political mainstream. Yet, we know less about how the political mainstream talks about radical right populists. Scholars assume a demonisation of populist radical right parties by the mainstream, which portrays the far-right outsiders as Nazis or fascists. This study assesses whether demonising discourses are indeed a common communicative element of Western European mainstream parties by analysing parties’ messages on Twitter in ten Western European countries during election campaigns. The findings indicate that demonising discourses are not as widespread as assumed in the literature but occur exclusively among some centre-left parties. In the article it is argued that historical contexts (experiences with fascist rule) and electoral breakthrough of radical right parties might explain why certain centre-lefts demonise their far-right competitors while others do not.