Setting the scene
McCarthyism surged in 1950, reaching its peak after Senator Joseph McCarthy of Wisconsin claimed on February 9, 1950, in Wheeling, West Virginia, that he had a list of 205 communists working in the State Department. McCarthyism—the practice of making unsubstantiated accusations of subversion and treason—had roots in the Red Scare following the Soviet atomic bomb (1949) and Communist victory in China (1949), plus the Alger Hiss conviction (1950) and Klaus Fuchs confession (1950).
What happened
McCarthy's charges, though never proven, tapped into genuine fears of Soviet espionage, which was real—Venona decrypts later confirmed Soviet spies in the U.S. government. McCarthy chaired the Senate Permanent Subcommittee on Investigations from 1953-1954, holding televised hearings that ruined careers through guilt by association, innuendo, and demands to name names. He targeted the State Department, Army, and Hollywood. The term 'McCarthyism' was coined by cartoonist Herblock in 1950.
Why it still matters
McCarthyism led to blacklists in Hollywood, loyalty oaths for government workers, and the imprisonment of the Hollywood Ten for contempt of Congress. It was fueled by the House Un-American Activities Committee (HUAC) and FBI Director J. Edgar Hoover. McCarthy was censured by the Senate in December 1954 after the Army-McCarthy hearings exposed his bullying tactics, and he died in 1957. McCarthyism became synonymous with demagoguery, witch hunts, and the suppression of dissent. It demonstrated how fear could undermine civil liberties and how media could both amplify and eventually check a demagogue.
Background
Loyalty oaths and blacklists spread fear.