How did the Trump administration change the place of religion in U.S. foreign policy? How did the guardrails of America’s foreign policy bureaucracy respond to a populist president? Drawing on firsthand experience in the State Department’s Office of Religion and Global Affairs during the Obama-Trump transition, David T. Buckley traces how the Trump administration’s populism affected the foreign policy bureaucracy, with significant implications for U.S. domestic and international politics. argues that under Trump, religion in U.S. foreign policy shifted from an implement of statecraft to a tool of populist political strategy. Populism constructs ideological bounds between “the people” and threatening outsiders, and embraces personalist governance while rejecting bureaucratic constraint. This domestic political logic, Buckley demonstrates, influenced foreign policy decisions and reshaped bureaucratic offices in the State Department and USAID. Populism also promoted international religious ties in a surprising range of settings, from Poland to India, Brazil to Russia. Buckley shows that the possibility of curbing these changes was limited by conditions in American democracy that predated the 2016 election, including norms of nonpartisanship among career officials, malleable legal institutions, and polarization in public opinion. A groundbreaking examination of Trump’s State Department, blending insider experience with original quantitative and qualitative data analysis, draws broader lessons for understanding the relationship between religion and democracy under populist rule.