Abstract Populist, protectionist, and progressive opposition to globalization are renascent among voters and politicians, but which of these ideologies have successfully inspired interest group mobilization? To answer this question, we collect original data on thousands of groups’ participation in highly organized coalitions opposed to US trade policy and globalization. Examining the types of groups that compose coalitions, variation in activation across issues, and coalitions’ written statements, we find that their motivations are mainly progressive, focused on the environment, human rights, economic justice, and reducing corporate power. We also focus on progressives’ labor union allies, showing that their participation in anti-trade coalitions is driven by both sincere progressive and classic protectionist motives. Thus, a progressive–labor alliance espousing mainly demands for fair trade, not plain protectionism, dominates public activism against US trade agreements. This interest group opposition has no match on the political right, suggesting that the recent efflorescence of populist anti-globalization may not last, even as progressive fair traders use their superior mobilization to endure.