Previous evidence highlights significant levels of animosity between supporters of radical right parties and those of other parties, contributing to overall affective polarization. However, there is limited understanding of the dynamics between the electoral emergence of radical right parties and affective polarization. We argue that out-party animosity is not only a potential consequence of radical right parties success but also a driver of their rise. Initially, centre-right partisans exhibiting relatively high levels of hostility towards left-wing voters are more likely to shift their support to an emerging radical right party, accounting for their positions on key issues. Subsequently, the irruption of a radical right party triggers a double defensive reaction among non-radical right party supporters: (a) the rapid development of strong antagonism towards radical right voters; and (b) a de-escalation of mutual hostility between left-wing and centre-right voters. We support these arguments with evidence from a Spanish panel dataset that captures the rise of the radical right party VOX.
