McCarthyism is the practice of making accusations of subversion or treason without proper regard for evidence. The term refers to U.S. senator Joseph McCarthy (R-Wisconsin) and has its origins in the period in the United States known as the Second Red Scare, lasting from the late 1940s through the 1950s. It was characterized by heightened political repression and a campaign spreading fear of communist influence on American institutions and of espionage by Soviet agents. After the mid-1950s, McCarthyism began to decline, mainly due to the gradual loss of public popularity and opposition from the U.S. Supreme Court led by Chief Justice Earl Warren. The Warren Court made a series of rulings that helped bring an end to McCarthyism.