McCarthy had access to the Venona Papers, but couldn't let on lest the Soviets find out. Thus, everyone he hounded was a bonafide Soviet mole.
After reading “Blacklisted by History” by M. Stanton Evans, I could see many parallels to what goes on in politics today. What happened at that time was that the inside-the-beltway crowd of that day all circled the wagons and turned on McCarthy because he was embarrassing too many of them and was threatening their careers with his revelations.
Remember that there were actually three investigations of Communists in the government. The McCarthy haters like to focus only on McCarthy's investigation to make it appear that McCarthy was an obsessed lone-wolf making up wild charges without any facts to back them up. But in reality there were two investigations prior to McCarthy's. The first investigation was the Dies investigation. When the Roosevelt administration failed to remove the Communists, there was another investigation several years later, that was the House Committee on UnAmerican Activities during the Truman administration. Again the Truman administration failed to clean out the Communists. Finally, McCarthy came on the scene a few years later and was still getting reports of Communists spying on the Army.
That is when the fat hit the fan. McCarthy was getting a lot of media attention and the American public was beginning to wonder why the problem was not solved after the other two investigations. This is when the Democrats came to the aid of their party and their beloved icon Franklin Roosevelt. The RINOs of that day joined forces with the Democrats and made a majority to censure McCarthy. Of course the major media of that day were worshipers of FDR but the people did not know of their bias back then. So when the Democrats and RINOs and the media turned on McCarthy, his life was over.
Watch how the media and the Democratic machine turn on the tea party people and the town hall protesters. They are doing to these citizens what they did to McCarthy fifty years ago.