Abstract In September 2021, President Biden announced that the Occupational Safety and Health Administration (OSHA) would require large employers to ensure workers are vaccinated against Covid-19 or tested weekly. Although widely characterized as ‘Biden’s vaccine mandate’, the policy could be described with equal accuracy as ‘OSHA’s testing mandate’. Some commentators speculated that reframing the policy as a testing mandate would boost support. This study investigates how framing effects shape attitudes toward vaccination policies. Before the Supreme Court struck down the vaccinate-or-test rule, we presented 1500 US adults with different descriptions of the same requirement. Reframing ‘Biden’s vaccine mandate’ as ‘OSHA’s testing mandate’ significantly increased support, boosting net approval by 13 percentage points. The effect was driven by changing the ‘messenger frame’ (replacing ‘Biden’ with ‘OSHA’) rather than changing the ‘message frame’ (replacing ‘vaccine mandate’ with ‘testing mandate’). Our results suggest that messenger framing can meaningfully affect public opinion even after a policy is widely known. Our study also reveals a potential cost of presidential administration when partisan divisions are deep. Framing a regulatory policy as an extension of the president can elicit strong—here, negative—reactions that may be avoidable if the policy is framed as the work of a bureaucratic agency.