To what extent do voters support election observation missions (EOMs) monitoring their elections? Building on but departing from prior work, we argue that citizens’ support for election observation missions likely depends on their partisanship. To test our argument, we conduct a survey experiment with a national sample of about 3, 500 Americans in the run-up to the 2020 United States presidential election. Respondents read an adapted news article about the deployment of common interventions in the upcoming election. To test our theoretical expectations, we randomize the partisan source endorsing the interventions. We find that respondents who self-identify as Democrats and Independents/Others are much less likely to support election observers when endorsed by Trump. In addition, Democrats are more likely to support election observers if they read that Biden approves of them. In contrast, Republicans are less likely to support an intervention if they read the same. Our results contribute to ongoing debates about how to promote and defend free elections in backsliding or democratizing countries and, more generally, to the literatures on election observation and public opinion.