McCarthyism is the practice of making accusations of subversion or treason without proper regard for evidence. It also means "the practice of making unfair allegations or using unfair investigative techniques, especially in order to restrict dissent or political criticism." The term has its origins in the period in the United States known as the Second Red Scare, lasting roughly from 1950 to 1956 and characterized by heightened political repression as well as a campaign spreading fear of influence on American institutions and of espionage by Soviet agents. These policies remote from the 1940's:
It originated with President Truman's Executive Order 9835 of March 21, 1947, which required that all federal civil service employees be screened for "loyalty." The order specified that one criterion to be used in determining that "reasonable grounds exist for belief that the person involved is disloyal" would be a finding of "membership in, affiliation with or sympathetic association" with any organization determined by the attorney general to be "totalitarian, Fascist, Communist or subversive" or advocating or approving the forceful denial of constitutional rights to other persons or seeking "to alter the form of Government of the United States by unconstitutional means."
"McCarthyism" soon took on a broader meaning, describing the excesses of similar efforts. The term is also now used more generally to describe reckless, unsubstantiated accusations, as well as demagogic attacks on the character or patriotism of political adversaries. During the McCarthy era, thousands of Americans were accused of being communists or communist sympathizers and became the subject of aggressive investigations and questioning before government or private-industry panels, committees and agencies. The primary targets of such suspicions were government employees, those in the entertainment industry, educators and union activists. Suspicions were often given credence despite inconclusive or questionable evidence, and the level of threat posed by a person's real or supposed leftist associations or beliefs was often greatly exaggerated. Many people suffered loss of employment and/or destruction of their careers; some even suffered imprisonment. Most of these punishments came about through trial verdicts later overturned, laws that were later declared unconstitutional, dismissals for reasons later declared illegal or actionable, or extra-legal procedures that would come into general disrepute.