Donald Trump's announcement that he will seek the presidency once more has brought a renewed focus on his worldview, his vision for the U.S. role in a complicated world. 'America First' has a long lineage in our politics, reaching back to a time when isolationism was the dominant foreign policy constituency in the country. In this episode, historian Christopher McKnight Nichols explores the continuities and major differences between the America First attitudes of the interwar period and today's Trumpist populism of the post-Cold War era.