“The [Communist] Party itself had focused on Hollywood starting in 1936, when V. J. Jerome, a cultural commissar, and Stanley Lawrence, a CP organizer, journeyed out to the West Coast to set up a movie-industry branch of the Party. ... John Howard Lawson, who ran the Hollywood branch, quickly understood that the collective process of moviemaking precluded the screenwriter, low man on the creative totem pole, from influencing the content of movies. As the Party's national chairman, William Z. Foster told the faithful in a secret meeting at Dalton Trumbo's house in 1946, 'We can't expect to put any propaganda in the films, but we can try to keep anti-Soviet agitprop out.' Lawson and Ring Lardner did run a writer's clinic that tried to analyze scripts from the viewpoint of a Marxist aesthetic, but submission and compliance were mostly voluntary, and the project never got very far.”

-- from “Naming Names” by Victor S. Navasky. The Foster quote comes from the author's interview with Alvah Bessie, one of the Hollywood Ten.