What explains variation in individual preferences for foreign economic engagement? Although a large and growing literature addresses that question, little research examines how partner countries affect public opinion on policies such as trade, foreign aid, and investment. We construct a new theory arguing that political side-taking by outside powers shapes individuals’ support for engaging economically with those countries. We test the theory using original surveys in the United States and Tunisia. In both cases, the potential partner country's side-taking in the partisan politics of the respondents’ country dramatically shapes support for foreign economic relations. As the rise of new aid donors, investors, and trade partners creates new choices in economic partners, our theory and findings are critical to understanding mass preferences about open economic engagement.