Amid threats to elections officials, disinformation about the security of U.S. voting systems and ongoing fallout from the Jan. 6 insurrection, scientists who study social movements have a lot to teach us about how we got here. In “Out of Hiding: Extremist White Supremacy and How It Can Be Stopped,” three sociologists who have spent their careers studying racist movements in the U.S. detail how extremist white supremacist ideas, “once tucked away in society’s corners,” became a mainstream and significant threat to democracy. Drawing on their decades of expe...