In 1950, Sen. Joseph McCarthy claimed that he had proof of a communist spy ring operating inside the government. Overnight, the explosive accusations blew up in the national press, but the details kept changing. Initially, McCarthy said he had a list with the names of 205 communists in the State Department; the next day he revised it to 57. Since he kept the list a secret, the inconsistencies were beside the point. The point was the power of the accusation, which made McCarthy’s name synonymous with the politics of the era.

For more than half a century, McCarthyism stood as a defining chapter in the worldview of American liberals: a warning about the dangerous allure of blacklists, witch hunts, and demagogues.