Joseph McCarthy gained public attention by

The correct answer here is by claiming to have a list of communists in the government.

Senator Joseph McCarthy is an infamous person in the history of the US politics as his opposition to and the hunt for communists led to severe problems in the US, in the period which is known as the Red Scare. McCarthy started a nation wide witch hunt for the communists supporters which did nothing except bully many of the people who had nothing to do with communism.

Joseph McCarthy gained attention by claiming that there were a large numbers of communists and Soviet spies in the US government. He was a politician who work as a senator from 1967 until 1957. He was famous during the Cold War period.