The politically passionate Sean Penn has no interest in running for office, yet he's a potent demagogue on the big screen. In a new adaptation of Robert Penn Warren's novel "All the King's Men," Penn stars as Willie Stark, a firebrand inspired by Depression era populist Huey Long, the slain Louisiana governor and U.S. senator. With a wild bush of hair, an at times indecipherable Southern drawl and the flailing arms and bellow of a fire-and-brimstone preacher, Penn imbues Stark with fearsome energy that's surprising in an actor better known as a follower of the Robert De Niro school of...