Why do some Americans assume social welfare programs primarily help immigrants? This pre-registered survey experiment explores the triggers for this perception. Respondents viewed generic policies differently when primed with specific concerns:

• Threat Prime Effects: A 'fiscal threat' framing significantly increased belief that immigrants are policy beneficiaries.

• No Effect from Cultural/Demographic Primes: Conversely, cultural or demographic threats had no impact on respondents’ beneficiary assumptions.

• Geographic Moderation: The fiscal threat effect varied by location but not based on prior attitudes toward immigration.

These findings reveal how specific concerns activate different assumptions about welfare policies. Importantly, the results show that when people assume immigrants are policy beneficiaries, their immigration attitudes become strong predictors of approving those policies.