What were the basic claims that Joseph McCarthy made after WWII ended?

Joseph P. McCarthy was a republican senator of Wisconsin, who tried for several years to expose left-wing and communists that according to him were disloyal. Those accusations were very convincing, and many Americans fell for them. Moreover, he was the first-term senator to won the election in 1946. In addition, while giving a speech in West Virginia at the Ohio County Women's republican club in 1950, he claimed to have a list of 205 well known members of the communist party who were, according to him, doing subversive activities. However, after some investigations no proof of such accusations were found.