In the 1950's, Joseph McCarthy used it to seek out and remove Communist from the US government. When you hear the term McCarthyism, that's what they referring too. Ironically, the Communist were able to gaslight the public (and Joe was a bit of an eccentric) and paint the situation as a sort of witch hunt against innocent people. In the end, he was unable to convict anyone, but the Venona Papers (released names of Communist agents found after the fall of the USSR) revealed that he was more or less right about the size and scope of the problems, and many of the people who were being investigated as well.

In the 1950's, Joseph McCarthy used it to seek out and remove Communist from the US government. When you hear the term McCarthyism, that's what they referring too. Ironically, the Communist were able to gaslight the public (and Joe was a bit of an eccentric) and paint the situation as a sort of which hunt against innocent people. In the end, he was unable to convict anyone, but the Verona Papers (released names of Communist agents found after the fall of the USSR) revealed that he was more or less right about the size and scope of the problems, and many of the people who were being investigated as well.