Social democratic parties across Europe have increasingly adopted restrictive immigration rhetoric in response to radical right challengers' electoral successes. The consequences of accommodation remain contested. This paper leverages a pre-registered quasi-experimental design exploiting within-individual variation from as-good-as-random exposure to UK Labour leader Keir Starmer’s “Island of Strangers” speech -- a major rhetorical turn toward anti-immigration positions. We find that exposure significantly altered perceptions of Labour, making it appear more anti-immigration and right-leaning. Crucially, these shifts carried electoral costs: support for Labour declined within individuals following the speech. While we detect no corresponding gains for the radical right Reform UK party, there is also no evidence that Labour’s adoption of nativist rhetoric diminished Reform’s appeal. Our findings highlight the risks of strategic convergence, showing that accommodation of exclusionary rhetoric by social democratic parties is electorally costly for them rather than for their radical right competitors.
Turnbull‐Dugarte et al. (Mon,) studied this question.