[237][238] Wisconsin Senator Joseph McCarthy accused the State Department of harboring communists and rode the controversy to political fame,[239] leading to the Second Red Scare,[240] also known as McCarthyism. McCarthy's stifling accusations made it difficult to speak out against him. This led President Harry Truman to call McCarthy "the greatest asset the Kremlin has" by "torpedo[ing] the bipartisan foreign policy of the United States."[241]
Charges that Soviet agents had infiltrated the government were believed by 78 percent of the people in 1946 and became a major campaign issue for Eisenhower in 1952.[242] Truman was reluctant to take a more radical stance, because he felt it could threaten civil liberties and add to a potential hysteria. At the same time, he felt political pressure to indicate a strong national security.[243] It is unclear to what extent President Truman was briefed of the Venona intercepts, which discovered widespread evidence of Soviet espionage on the atom bomb project and afterward.[244][245] Truman continued his own loyalty program for some time while believing the issue of communist espionage was overstated.