Final answer:
The Army-McCarthy Hearings, investigating Communist subversion in the U.S. Army, led to McCarthy's downfall.
Step-by-step explanation:
The hearings to investigate Communist subversion in the U.S. Army led to McCarthy's downfall. These hearings, known as the Army-McCarthy Hearings, took place from April to June 1954 and were televised, allowing the American public to witness McCarthy's use of intimidation and innuendo. As a result, the public rejected McCarthy's approach, and in December 1954, the U.S. Senate officially condemned his actions with a censure, ending his prospects for political leadership.