In recent years, substantial scholarly attention has been devoted to examining the impact of far-right parties’ rhetoric and positions on mainstream right-wing parties. However, comparable analyses of the interactions within the left bloc of party politics remain relatively underexplored. This paper investigates whether radical left parties influence centre-left parties to adopt more leftist (i.e., radical) rhetoric and positions. While radical left parties, often situated in opposition, advocate clear and uncompromising left-wing stances, centre-left parties typically pursue more pragmatic, moderate positions to maintain broad electoral appeal and coalition potential. The extent to which these radical voices shape the rhetoric and positions of centre-left parties is a critical question for understanding intra-bloc dynamics within the left. This question becomes even more salient in light of the crisis faced by social democratic parties in the early 21st century and the concurrent electoral rise of several radical left parties, some of which have entered governing coalitions. To address this issue, we analyze plenary speeches delivered by left and centre-left MPs in national parliaments across 13 European countries where radical left parties maintain a significant presence. Drawing on data spanning 2009 to 2019, we employ a longitudinal approach to examine whether radical left MPs’ interventions influence center-left MPs to engage with similar issues or adopt comparable rhetoric. By leveraging textual data, this study tracks shifts in political focus and rhetorical alignment over time, contributing to a deeper understanding of left-bloc interactions and their implications for party politics.
