Joseph Raymond "Joe" McCarthy (November 14, 1908 – May 2, 1957) was an American politician who served as a Senator from Wisconsin.  It is to him we attribute the term "McCarthyism" -- reckless, unsubstantiated accusations, as well as demagogic attacks on the character or patriotism of political adversaries.  This was one of the legacies of Joseph who was son of Bridget (Tierney) from Tipperary. His father, Timothy McCarthy, was born in the United States, the son of an Irish father and a German mother.

 "John Earl Haynes concluded that, of 159 people identified on lists used or referenced by McCarthy, evidence was substantial that nine had aided Soviet espionage efforts. He suggested that a majority of those on the lists could legitimately have been considered security risks, but that a substantial minority could not. Many other scholars, including some generally regarded as conservative, have opposed these views." From Wikipedia

Above, Edward R. Murrow: "A Report on Senator Joseph R. McCarthy"