What actions of senator joseph mccarthy worsened the national hysteria about communism?

List of names of communist spies in the government--Jospeh McCarthy claimed he had a list of people's names who were spies for the USSR and were working in the government. 

Joseph McCarthy, a Senator from Wisconsin, claimed to have the names of spies in the government. He then led an investigating committee where hearsay and rumors were the evidence against people named as being spies. It was later found in the investigation of Joseph McCarthy that he never had a list of names and he was bullying and threatening people to admit to untrue information.