PALM BEACH, Fla. - Bushies beware. There is a new force on the campaign trail, and its name is Michael Moore.

"Fahrenheit 9/11," the Oscar-winning filmmaker's scalding indictment of the Bush administration's response to Sept. 11, 2001, and prosecution of war in Iraq, may be the most energetic political endorsement John Kerry could hope for.

The film, which won the Golden Palm at the Cannes Film Festival last month, arrived in theaters Friday riding a wave of publicity the likes of which most documentarians can only dream about. Disney CEO Michael Eisner's decision not to distribute the film through Miramax - ostensibly in an effort to stay above the election-year political fray - guaranteed an even wider audience.

As in his previous documentaries, many of Moore's arguments are loaded, and fraught with calculated imagery. While this time he refrains from casting himself in the central role - that hot seat is reserved for George W. Bush - it is still Moore's singular voice that animates his film. And when it comes to this subject, the passions are not hard to stoke.

That he manages to fan those flames with a great deal of comedy, however, makes him much more than a mere blunt instrument. "Fahrenheit 9/11" may be preaching to the choir, but Republican strategists should be concerned about those pews of undecided voters who line up to see the film.

Ever since his 1989 breakthrough, "Roger & Me," Moore has cultivated a persona - canny yet guileless, smart but unsophisticated - that is key to his appeal. He knows that humor is the elixir that helps wash down the bitter pill of his stridency, and in the president of the United States, he has found a subject ripe for amusement.

Moore often plays the rube, but his skillfull use of banjo music, for example, confers the role of bumpkin on Bush, beginning with the prologue, set in November 2000, in which he asks, "Was it all just a dream?" For Moore and roughly half the country, the implication is that it was more of a nightmare.

From his opening salvo against an "illegitimate president," as Moore infamously taunted from the stage of the Academy Awards in 2003, the belittling of Bush only gets worse.

Moore's litany stretches from the Bush inauguration to the present, including ties between Bush family oil interests and those of the Saudi elite, including the bin Laden family; the Department of Homeland Security and its color-coded alert system; the Patriot Act; and the war in Iraq and its aftermath.

One of the film's dominant themes - the president's innate lack of seriousness - is established early and repeatedly sent up with incriminating footage. We are reminded of the spring and summer of 2001, when, according to The Washington Post, Bush spent 42 percent of the first eight months on vacation.

Scenes of the president at work and play also serve to underscore his frequent ineloquence and questionable sense of gravity. "I call on all nations to stop the terrorist killers. Thank you," he says, as the camera pans back to reveal the leader of the free world on the golf tee. Smirking, he adds, "Now watch this drive."

Moore modulates the humor and pathos with skill. He scrupulously avoids familiar Sept. 11 news footage - there isn't a single shot of fire or of either tower, standing or fallen - instead powerfully suggesting the emotions of the day by lingering on the faces of bystanders in Lower Manhattan as they strain to comprehend it.

And his mini-profile of a military mother - who goes from touting the benefits of a military career in her role as a jobs counselor in the impoverished community of Flint, Mich., to becoming a vocal critic of the war in Iraq after losing her son there - is one of the film's most poignant undercurrents.

Although his improbably jolly demeanor can't mask his real fury, Moore is at his best when serving up laughs, convincingly implying that they are the only way of dealing with many of the more incomprehensibly absurd details arrayed before us.

He trots out some familiar stunts - ambushing congressmen on the street to urge them to enlist their offpsring in the military (not one does, of course) and boarding an ice cream truck to read portions of the Patriot Act to members of Congress over the loudspeaker after learning that most didn't read the controversial legislation for themselves before approving it.

In addition to the deftly employed banjo, other dead-on musical choices include The Go-Gos' "Vacation" (over footage of Bush's first 200 days in office) and "The Theme from The Greatest American Hero" ("Believe it or not, it's just me") over the president's "Top Gun" moment aboard an aircraft carrier proclaiming "Mission Accomplished" in Iraq.

"This is an op-ed piece, it's not a news article," Dev Chatillon, a former New Yorker attorney who heads up Moore's fact-checking operation, recently told The New York Times.

"Fahrenheit 9/11" may be taken either as screed or scripture, depending on your political persuasions. Moore's strength is that, either way, you can't ignore it.