How do foreign rivals perceive and respond to heightened domestic polarization in the United States? The conventional thinking is that polarization weakens and distracts the United States, emboldening its adversaries. However, untested assumptions underlie this claim. We use two strategies to explore mechanisms linking domestic polarization and international rivalry. First, we field a survey experiment in China to examine how heightening perceptions of US polarization affects public attitudes toward Chinese foreign policy. Second, we investigate how US rival governments responded to an episode of extreme partisanship: the US Capitol attacks on January 6, 2021. Drawing on Integrated Crisis Early Warning System event data, we explore whether foreign rivals increased hostility toward the United States following the Capitol riots. Both studies fail to show robust evidence for the Emboldening Hypothesis. Extreme polarization has other negative consequences for American foreign policy, but we find no evidence that it makes adversaries materially more assertive toward the United States.