In 1940, a Los Angeles jury released testimony linking James Cagney to the Communist Party, or at least to "communist members, sympathizers or heavy contributors." He had supported something called the Hollywood Anti-Nazi League, apparently not knowing that it was a Soviet front.

Until old age, Cagney was an unapologetic liberal, who had backed environmental and labor causes. But he was not a communist. Martin Dies, the red-hunting congressman from Texas, eventually gave Cagney a clean bill of political health.

Still, it may have been no coincidence that shortly after the headlines hit, an actor mostly known for gangster roles starred in the most over-the-top patriotic movie musical of all time, "Yankee Doodle Dandy." There he played George M. Cohan, another Irish-American showman from an earlier generation and composer of such upbeat Americana as "Give My Regards to Broadway," "You're a Grand Old Flag" and, of course, "The Yankee Doodle Boy." (Movie plot to the contrary, Cohan was born on the third of July, not the fourth.) Posters for the film showed Cagney in an Uncle Sam hat.

A monumentally talented actor and dancer, Cagney refused to be pushed around artistically or politically. He was a sympathizer, all right — of the working class. In his youth, Cagney had held such jobs as a bellhop, library worker and night watchman. "I feel sorry for the kid who has too cushy a time of it," he once said.

Cagney sent money to striking farm workers in the San Joaquin Valley. He helped found the Screen Actors Guild — representing overworked and unpaid actors — and later served as its president. He repeatedly fought his Hollywood bosses, often walking off sets. Jack Warner of Warner Bros. called Cagney a "professional againster."

In 1932, Louis B.

Mayer of MGM led Hollywood moguls in a campaign to defeat Socialist-turned-Democrat Upton Sinclair, then running for governor of California. They tried to force their stars to "donate" a day's pay to help Sinclair's Republican foe, Frank Merriam. Cagney vowed that if he was forced to give a day's pay to Merriam, he'd give a week's pay to Sinclair. Jean Harlow, Edward G. Robinson and Katharine Hepburn joined the rebellion.

Though from seemingly similar backgrounds, Cohan and Cagney differed in social outlook. Cohan disapproved of actors strikes. The movie features a fictional character named Mary as the composer's one and only (to go with the Cohan song "Mary Is a Grand Old Name"). In real life, Cohan had two wives. Cagney, on the other hand, entered one marriage that lasted from 1922 to his death in 1986. Cagney loved rural life and ran a working farm. But the man who wrote "Forty-five Minutes From Broadway" seemed most comfortable no farther than five. The Lambs Club was more his speed.

"Yankee Doodle Dandy" opened 70 years ago. It is Cagney's toughness that makes the movie — with its pounding patriotism verging on jingoism — not only bearable but lovable. The romantic scenes may be starved of passion. And some of the cute but boring comedy bits had me fumbling for the fast-forward button. But the Cohan songs are fabulous, as is Cagney's interpretation of them.

Given the swirling rumors that Cagney had strayed over the communist line, the decision to star in "Yankee Doodle Dandy" must have been a good career move. But you sense that the inner Cagney was totally onboard. In that last honestly emotional scene, Cagney played an elderly Cohan marching beside American soldiers headed for World War II and singing his World War I song "Over There." When Cagney's eyes watered just a bit, it may not have been acting. I know mine did.