Final answer:
Senator Joseph McCarthy of Wisconsin led a campaign against alleged communists in the U.S. government, an era dubbed McCarthyism. He claimed to have a list of communists in the State Department without providing evidence. The unfounded anti-Communist crusade contributed to widespread fear and suspicion in the U.S.
Step-by-step explanation:
The Senator who led the infamous campaign to root out alleged communists within the U.S. government was Joseph McCarthy. McCarthy, a Republican from Wisconsin, capitalized on the fears of communism to secure his political career. In 1950, he claimed to have a list of communists working within the State Department; however, he failed to provide any concrete evidence to support his claims. This period of American history, characterized by accusations without proper proof, became known as McCarthyism, an era marked by the spread of fear and mistrust.
McCarthy's charges that the Democratic Party was complicit in allowing communists to infiltrate the government led to a wide-reaching, unfounded anti-Communist campaign. Important Republicans of the time saw McCarthy as an asset for the party, especially leading into the 1952 elections. However, McCarthy's inability to substantiate his claims eventually led to ridicule and his eventual censure by the Senate. The term 'witch hunt' often refers to his tactics of making serious allegations without proper evidence, which resulted in a state of fear and suspicion throughout the nation. This era also saw the likes of J. Edgar Hoover, head of the FBI, taking extreme measures against those suspected of being communists or sympathizers, further fueling the anti-Communist sentiment.