What drives anti-colonial activism? This study examines how perceived threats from internal French migration influenced support for both independence and political violence in the French overseas territory of New Caledonia, ultimately leading to widespread unrest there in May 2024. Through a survey experiment with 1,200 indigenous respondents, the research analyzed how different framings of migration patterns affected indigenous Kanak attitudes toward separatism and contentious action. The findings reveal that fears of demographic displacement from internal French migrants significantly increased support for independence and political violence, particularly among younger Kanaks. These results demonstrated how nativist sentiments can drive left-wing decolonization movements, despite typical associations of nativism with right-wing politics in Western contexts. This apparent paradox highlights how similar psychological mechanisms of demographic threat can fuel both anti-immigrant politics in Western metropoles and indigenous resistance in colonial settings. The research exposes the shared psychological roots of nativism and indigenous decolonial politics, challenging the conventional opposition between these movements and suggesting both spring from similar anxieties about demographic marginalization.