TORONTO (AP) _ 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 quiet menace.

"At first, the most intimidating part of it was probably the size of the character, not just physically, but in other ways. Vocally," Penn said in an interview at the Toronto International Film Festival, where "All the King’s Men" premiered in advance of its theatrical debut Friday.

Penn, 46, studied footage of Long. He travelled Louisiana to take in the bridges, roads and other public works Long built. He talked with people, who still recall Long as a Robin Hood taking back from the rich and redistributing to the poor. He observed evangelical clergy in Long’s old haunts to duplicate their cadence. And he sampled the cuisine.

"Eating a lot of Louisiana food, bit by bit, getting some of the physical size to it," Penn said. "Somewhere about the day before we started shooting, I felt ready to go. It’s pretty much like that for me. Terrified until then."

While Penn has bitterly criticized U.S. President George W. Bush, toured Iraq to observe the war there and helped rescue workers with door-to-door searches for survivors after Hurricane Katrina swamped New Orleans, he said he would not become one of those actors who goes into politics himself.

"You know what the honest truth is? I don’t want to," Penn said. "It’s hard enough to go out there and party at a film festival and shake so many hands and smile, you know? I mean, forget it."

"All the King’s Men" _ which co-stars Jude Law, Kate Winslet, Anthony Hopkins, Patricia Clarkson and Mark Ruffalo _ follows the rise of an idealist from local rabble-rouser against the political establishment to governor, hero to the downtrodden and Machiavellian power broker, who uses dubious methods in his quest for the common good.

When "All the King’s Men" writer-director Steve Zaillian finished the script, Penn was the first person he thought about for the role.

"Because he’s the best, I think. As simple as that," Zaillian said. "I think he’s the best actor out there."

"Sean’s talent, his gravitas, his joie de vivre. It’s all of that. That’s what that part requires," said co-star Clarkson, a Louisiana native who plays Stark’s press secretary and mistress. "It requires someone large and delicate all at once, and Sean has all of it."

Broderick Crawford won the best-actor Academy Award as Stark in the 1949 adaptation of "All the King’s Men." (The film also won the best-picture Oscar.) Penn probably will not mind that the early buzz this time is that his "All the King’s Men" performance may be too over-the-top to grab awards attention.

Penn won the best-actor Oscar for Clint Eastwood’s 2003 drama "Mystic River," and no longer has to endure questions about being one of the great actors of his generation who has yet to win a trophy. Often openly disdainful of awards, Penn skipped the Oscar ceremony the three previous times he was nominated, for "Dead Man Walking," "Sweet and Lowdown" and "I Am Sam."

Penn made nice with the Oscars three years ago, coming to preliminary awards events and showing up on the big night itself, when he went home with his statuette.

Why did he go that night?

"Two words, baby. Clint Eastwood," Penn said. "Whatever makes Clint happy, I do."

Part of a show business family that includes brother Michael, a musician, Penn and wife Robin Wright Penn have two children and live in Northern California, far from the celebrity-mad crowds he contended with in his first marriage to Madonna. Penn and his family have been coping with the loss of his brother, actor Chris Penn, who died last January of an enlarged heart. Penn quietly and tersely handles questions about how it has affected the family.

"A good friend of mine described it best when I saw him. He came over. He said, ‘It’s a stinker. It’s a stinker,"’ Penn said. "That’s what it is."

Like Eastwood, Penn loves to direct. He previously made the sobering dramas "The Indian Runner," "The Crossing Guard" and "The Pledge," the latter two starring Jack Nicholson. Penn now is directing "Into the Wild," starring Emile Hirsch in the true story of Christopher McCandless, a young idealist whose journey to Alaska ends in tragedy.

Penn said he wishes he could give up performing and remain behind the camera full time, but he needs the acting income because he’s a soft touch for charitable causes.

"Let me tell you what happens. You go public politically on anything, you start getting phone calls from everybody who needs money for various things," Penn said. "You get not rich real fast."

In the aftermath of the Sept. 11, 2001, terrorist attacks and the U.S. war in Iraq, Penn said filmmakers have become energized to take on political subjects again, as they did in the 1960s and ’70s amid the Vietnam War and the Watergate scandal.

"It’s not surprising. It’s their daily life and conversations over coffee. It’s affecting everything we do. It’s been the history of film in the past every time we suffer," Penn said.

"The biggest problem is, when we have a choice of being comfortable or not, we choose comfortable all the time. It’s overrated. And it certainly doesn’t allow for much art. And now we’re uncomfortable, so more art’s going to come out of it."