While the literature on populist parties has initially stressed their nature as “challengers”, a more recent interpretation conceives of them as the “new mainstream”. This article argues that both these approaches need revisiting. The first one fails to recognize that populist radical right parties are a constant and well rooted presence in the 21st century, and are increasingly accessing governments. The second looks at the supply-side of populism and is based on a purely functional definition of the “mainstream”. We argue that, in order to evaluate whether a phenomenon is in fact “mainstream”, both its supply- and demand-side components must be studied. Therefore, we introduce an “attitudinal” component to the definition of the “mainstream. By relying on the last wave of the European Social Survey, we apply our bi-dimensional definition of the “mainstream” to assess whether the populist radical right ideology can be deemed to be as such in attitudinal terms across 21 European countries. We conclude that populist radical right parties should be seen as the new “outer mainstream”: their supply-side component is part of the mainstream, while their ideology (the demand-side) remains firmly outside.
