The death of Senator Joseph McCarthy in 1957 left a vacuum in the conspiracy-minded wing of the American conservative movement. In 1958, retired candy-manufacturer Robert Welch, who suspected that the Wisconsin Senator had been murdered by the Communist conspiracy, formed the John Birch Society to continue McCarthy's mission. The Society took its name from Captain John Birch, a young American soldier killed by Chinese Communists in 1945 and regarded by Welch as the first American martyr of the Cold War.

Like McCarthy, the Birch Society offered an ideology that combined anti-Communism with anti-liberalism and populism. For the Birch Society, Communism included not just the external threat of the Soviet Union, but also the more pernicious danger of internal subversion by the "creeping socialism" of the New Deal. Liberals and moderate conservatives are regarded by the Society as being either Communist agents or unwitting dupes. Especially dangerous are...