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Political and religious views

Kelly was a lifelong supporter of the Democratic Party. His period of greatest prominence coincided with the McCarthy era in the US. In 1947, he was part of the Committee for the First Amendment, the Hollywood delegation that flew to Washington to protest at the first official hearings by the House Committee on Un-American Activities. His first wife, Betsy Blair, was suspected of being a communist sympathizer, and when United Artists, which had offered Blair a part in Marty (1955), were considering withdrawing her under pressure from the American Legion, Kelly successfully threatened MGM's influence on United Artists with a pullout from It's Always Fair Weather unless his wife was restored to the part. He used his position on the board of directors of the Writers Guild of America West on a number of occasions to mediate disputes between unions and the Hollywood studios.

He was raised as a Roman Catholic and was a member of the Good Shepherd Parish and the Catholic Motion Picture Guild in Beverly Hills, California. However, after becoming disenchanted by the Roman Catholic Church's support for Francisco Franco against the Second Spanish Republic during the Spanish Civil War, he officially severed his ties with the church in September 1939. This separation was prompted, in part, by a trip Kelly made to Mexico in which he became convinced that the church had failed to help the poor in that country. After his departure from the Catholic Church, Kelly became an agnostic, as he had previously described himself.