Clay Risen is a reporter at The New York Times, a member of the Society of American Historians, and a fellow at the Perry World House at the University of Pennsylvania. His new book is "Red Scare." He also wrote three previous works on American history, including "The Crowded Hour," a New York Times Notable Book of 2019 and a finalist for the Gilder-Lehrman Prize in Military History, "The Bill of the Century," a finalist for a 2014 NAACP Image Award, and "A Nation on Fire....