Party Time: The Effect of Partisan and Nonpartisan Media Messages on Support for Packing the US Supreme Court

ABSTRACT Objective This study assessed how different types of framed media messages—nonpartisan, partisan, and mixed—affect public support for Supreme Court reform, specifically the proposal to add justices to the bench (Court packing). Methods We conducted a pre‐registered survey experiment with approximately 1500 respondents recruited via Prolific. Participants were randomly assigned to one of seven conditions, including a control, nonpartisan‐only, partisan‐only, or combined frames, all presented in the format of brief news articles. We measured respondents’ support for Court packing and analyzed treatment effects using OLS regression. Results Anti‐Court packing messages consistently reduced support for reform, regardless of partisanship. Pro‐reform messages—especially partisan ones—were largely ineffective at increasing support for Court packing. Nevertheless, partisan framed messages moved respondents in ideologically congenial ways compared to the effects of nonpartisan messages. Conclusion In a polarized media environment, anti‐reform messages are more persuasive than pro‐reform ones, and out‐party cues are more powerful than messages tapping universally shared values. These findings suggest that partisan identity strongly conditions how citizens respond to messaging about institutional reform.