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Though Cagney claimed in his autobiography he had no political view when he was younger, the Fanzines in the 1930's says he views were radical. The view was exaggerated by his wranglings with Warners at the time, his joining of the Screen Actors Guild, and his revolt against the Merriam tax.
Cagney supported the Thomas Moody's defense fund but he was repelled by the behavior of some of Mooney's supporters at the rally. During the Spanish Civil War, Cagney gave money for the Spanish Republican Army ambulance. Cagney also became involved with a liberal along with Ronald Reagan however both quit the same night.
Cagney was accused of being a Communist sympathizer in 1934, and again in 1940. The 1934 accusation came about form a letter from a local communist official found by police alleging that Cagney would new members to meetings. Cagney denied the accusation. Lincoln Steffens backed him up saying the money he gave was to help striking cotton workers in San Joaquin Valley. The 1940 accusation was about the donated money for the striking cotton workers. Cagney was cleared of the charges.
Cagney became President of the Screen Actors Guild in 1942. He took an active role in the Guild's work against the Mafia. Around this time the Mafia had taken an active interest in the movie industry. Because the Mafia couldn't scare Cagney and the Guild off, they called Billie to tell her Cagney was a dead man. Cagney said they did send a hit man to kill him by dropping a heavy light onto his head. Upon hearing about the rumor of the hit, George Raft canceled the hit.
During World War 2, Cagney took part in raising war bonds in racing exhibitions at the Roosevelt Raceway and sold seats for the premiere of 'Yankee Doodle Dandy. He even let the Army practice maneuvers at his Martha's Vineyard farm. After the war, Cagney got involved with the presidential campaigns. Cagney supported Ronald Reagan's campaign.
As Cagney got older, he became more and more conservative. Cagney regarded the move totally natural because of the undisciplined elements in our country referring to the hippies and their mind set.