External Threat and Support for Secession: Evidence from Greenland amid U.S. Annexation Claims

How do external threats affect public support for secession? Sovereignty debates rarely happen in a domestic vacuum, because outside actors can alter the perceived viability of exit through coercive claims and security signaling. I argue that external threats reduce support for secession by raising the perceived costs and uncertainty of sovereignty, with larger effects in more capacity-constrained places where the per capita burden of independence is higher and buffers against shocks are thinner. I test these expectations in Greenland, exploiting a unique empirical opportunity in which a salient U.S. annexation threat escalated in a shock-like manner between two nationwide elections held three weeks apart in 2025. Using locality-level electoral returns, I find that pro-independence voting declined sharply in response to U.S. threats, and the decline was concentrated in smaller and lower-income settlements. The findings show that in great power competition, external threats can quickly shift support for the territorial status quo, and that local capacity conditions where the effects are largest.