Between 1950 and 1954, latterly as chairman of a government committee, he was the instigator of widespread investigations into alleged Communist infiltration in US public life. Although most of those accused during the period of ‘McCarthyism’ were not in fact members of the Communist Party, many of them were blacklisted, lost their jobs, or were otherwise discriminated against in a mood of hysteria, which abated only after the public censure of McCarthy in December 1954.