Some observers have approvingly claimed that the second Trump administration heralds a realist revival in American foreign policy. Writing in Foreign Affairs , Robert O'Brien, who served as national security adviser in the first Trump administration, eagerly promised “the return of realism with a Jacksonian flavor.” This view is gravely mistaken. Realists often disagree, sometimes sharply, about the best course of action, so it is not easy to say what a “realist foreign policy” is. But it is