Final answer:
Senator Joseph McCarthy was powerful because he exploited fears of communist infiltration, had strong political support, and possessed a charismatic speaking style.
Step-by-step explanation:
Senator Joseph McCarthy was powerful due to a combination of factors. Firstly, he exploited fears of communist infiltration in the United States, which resonated with many people during the Cold War era. Additionally, McCarthy had strong political support from prominent Republicans like Senator Robert Taft and Congressman Richard Nixon, who saw him as an asset in targeting Democratic politicians. Lastly, while McCarthy's tactics were later discredited, he had a charismatic speaking style that allowed him to captivate audiences and gain public support.