Why is the populist radical left and right on the rise across western Europe? Integrating theories on changing socio-political conflict with arguments about crises of political representation, we contend that electoral support for radical right and radical left parties is rooted in two distinct sets of socio-structural factors, but their translation into electoral choice is in both cases conditioned by the individual political discontent that originates in specific political dynamics. Relying on the European Social Survey (ESS) covering the period from 2002 to 2016 and Parlgov data, we show that the lack of responsiveness of mainstream parties to the changing social conflict structure provides critical opportunities for new challengers from both the radical left and the radical right, while voters’ political discontent only works to heighten their success when these parties are in opposition. Our article contributes not only by offering an integrative account of the electoral appeal of the radical right and radical left parties. In emphasising the largely similar nature of short-term, political factors that condition the translation of the different sets of long-term, structural determinants into opting for these parties, critically, this article also contributes to understanding the electoral success of radical challengers across western Europe.