This thesis investigates the variation in the electoral performances of right-wing populist parties in the Benelux region (i.e. Belgium, the Netherlands and Luxembourg). Despite numerous historical and political commonalities, right-wing populist parties have been more successful in the Netherlands and Flanders (i.e. the northern, Dutch-speaking part of Belgium) than in Luxembourg and Wallonia (i.e. the southern, French-speaking part of Belgium).

The thesis sets out to explore ‘conventional’ explanations, including socio-economic indicators (i.e. demand-side factors), and institutional as well as party organisational features (i.e. supply-side explanations). The analysis suggests that demand for right-wing populist parties is relatively constant across the Benelux region, whereas the supply of such parties has been weaker in Wallonia and Luxembourg than in Flanders and the Netherlands. However, supply-side explanations cannot fully account for the variation in the electoral performances of right-wing populist parties. The research therefore focuses on the wider context in which party competition takes place by highlighting the role of mainstream parties and the media; taken together, they act as gatekeepers in the sense that they can facilitate or hinder access into the electoral market. By politicising issues that are traditionally ‘owned’ by the populist radical right (notably immigration), they can create favourable opportunity structures for right-wing populist parties to thrive.

Empirical support is drawn from party manifestos as well as semi-structured interviews with media practitioners and politicians. In Flanders and the Netherlands, the decline of mainstream parties as well as changes in the media landscape have contributed to the radicalisation of the political discourse, which has created fertile ground for right-wing populist challengers. By contrast, Wallonia and Luxembourg have remained relatively immune to these tendencies: mainstream parties have (thus far) managed to hold on to their core electorates, while the media are generally hostile to the populist radical right.

The thesis complements existing theoretical explanations by moving beyond the traditional demand- and supply-side framework. The findings suggest that the reactions of mainstream political parties and the media are crucial to understand the variation in the electoral performances of populist radical right parties in Europe.