Shortly after World War II, Congress' House Committee on Un-American Activities began investigating Americans across the country for suspected ties to communism. The most famous victims of these witch hunts were Hollywood actors, such as Charlie Chaplin, whose "Un-American activity" was being neutral at the beginning of World War II. By the late 1950s, the hysteria had waned, recognized in large measure as an overreaction.

Another factor was the disrepute the Red Scare fell into because of the antics of Wisconsin Senator Joseph McCarthy. McCarthy had made waves in 1950 by telling the Republican Women's Club in Wheeling, West Virginia that he had a list of dozens of known communists working in the State Department. The political theater helped Senator McCarthy become the most prominent anti-communist crusader in the government, and the Rosenberg case only further emboldened him. McCarthy continued to claim he held evidence suggesting communist infiltration throughout the government, but anytime he was pressed to produce his evidence, McCarthy would not name names. Instead, he'd accuse those who questioned his evidence of being communists themselves.

McCarthy's rise made it possible for him to continue lobbing accusations against people, but the Senator finally met his match when he went after the Army. As chairman of the Senate Committee on Government Operations, McCarthy summoned decorated World War II veterans and challenged their loyalty, and when he openly suggested World War II hero Brigadier General Ralph W. Zwicker was a communist during one hearing, the military had enough. In April 1954, the committee hearings were widely televised, and Americans watched Army members demand that McCarthy name names and provide evidence. On June 9, 1954, McCarthy was humiliated by the Army's legal representative, Joseph Nye Welch, who repeatedly demanded that McCarthy produce the list of alleged communists in the US Army. As McCarthy tried to wiggle out of the challenge, he finally named Fred Fisher, who had been affiliated with the National Lawyers Guild during law school, an organization that FBI Director J. Edgar Hoover attempted to have the Attorney General designate as a communist front. Enraged, Welch responded, "Until this moment, Senator, I think I have never really gauged your cruelty or your recklessness. Fred Fisher is a young man who went to the Harvard Law School and came into my firm and is starting what looks to be a brilliant career with us...We know he belonged to the Lawyers Guild. Let us not assassinate this lad further, Senator. You've done enough. Have you no sense of decency, sir? At long last, have you left no sense of decency?" Welch received an ovation from the gallery, and McCarthy had been publicly and permanently repudiated. He would be censured by Congress, and he would die just a few years later.

Though anti-communist sentiment in the 1950s is often derisively dismissed as McCarthyism, there was some basis for the era's fears. The Communist Party in the United States was funded by the Soviet Union; its leaders were paid by the Soviets, and several were agents of the Soviet intelligence apparatus. Still, as a small elite group that was able to place individuals in positions of power, they did present a potential threat to the security of the country, and there were several spy rings operating in America at the time.