Who were the leading practitioners of the 1950's red scare?

Senator Joseph McCarthy was the leading figure in the 1950s Red Scare, or witch hunt for Communists in the government. The Senator from Wisconsin had nothing to do with the blacklisting of artists by the House UnAmerican Activities Committee, another group searching out Communists or "fellow travelers." McCarthy claimed that there were known communists in the State Department. He held investigations and hearings and ruined many careers. Presidents Truman and Eisenhower so feared his influence with the public that they did nothing to stop him. When McCarthy attacked the US Army as a hotbed of communist activity, the Senate finally censored him and he died a broken politician.