Jon Stewart, fake journalist and proud of it, keeps insisting he's just a comedian.

Night after night, "The Daily Show" host lampoons President Bush as a tongue-tied bumbler, Donald Rumsfeld as a mad ranter who resembles "Pete the crazy guy outside my apartment," the war in Iraq as a giant "Mess O' Potamia" and the reporters who cover the presidential race as self-important clods.

Such sharp-edged skewering has turned the Comedy Central funnyman into a cultural phenomenon who, despite his protestations, seems to be having some undefined, irony-drenched influence on how the campaign is perceived. He's been on the cover of Newsweek and now graces the cover of Rolling Stone. His "America (The Book)" is the nation's top seller. He has analyzed the media as Ted Koppel's guest, dissected the party conventions as Tom Brokaw's expert and ripped into his hosts on "Crossfire" for presiding over "theater" and "partisan hackery."

"There's a difference between making a point and having an agenda," Stewart says. "We don't have an agenda to change the political system. We have a more selfish agenda, to entertain ourselves. We feel a frustration with the way politics are handled and the way politics are handled within the media."

Stewart, 41, has announced that he plans to vote for John Kerry, who made one of his few television talk show appearances in recent months on "The Daily Show." That might come as little surprise to viewers who have watched Stewart relentlessly mock Bush while just poking gentle fun at Kerry's ponderous speaking style.

All of which means "the Jon Stewart backlash should start right about now," says Ana Marie Cox, also known as Web satirist Wonkette. "Stewart has pretty much painted a target on his chest with his 'Crossfire' appearance. To say his is just a comedy show is a cop-out in a way. He's gotten so much power. So many people look to him that you can't really be the kid in the back throwing spitballs."

But with a program that more than doubles the audience of "Hardball" with 1.2 million viewers -- many of them in the hard-to-reach younger generation -- Stewart's comedic spitballs are leaving their mark. Half of 18- to 29-year-olds say they regularly or sometimes learn things from late-night comedy shows, a Pew Research Center survey found. Fourteen percent of "Daily Show" viewers say they are liberal and just 2 percent conservative. Only 17 percent of the program's audience is over 50.

Stewart disputes the notion that younger viewers turn to him for news, and the Annenberg Public Policy Center backs him up. "Daily Show" fans are more knowledgeable about current events than those of other comedy shows, the center found, rivaling newspaper readers and network news viewers.

"It's not fake news," Stewart says. "We are not newsmen, but it's jokes about real news. We don't make anything up, other than the fact we're not actually standing in Baghdad. . . . The appeal of doing the show is that it's cathartic."

In a year when Howard Stern, Michael Moore and Bruce Springsteen have used their entertainment platforms to rip the president, Stewart provides an ideal venue for politicians -- especially Democrats -- looking to demonstrate hipness. Kerry was happy to appear because Stewart "has got a big audience that is different from the audience that watches 'Meet the Press' or 'Nightline,' " says spokesman Joe Lockhart. "Jon Stewart has a huge following on college campuses," and the format is "not as confrontational" as on hard-news shows.

Little wonder, then, that John Edwards announced his candidacy on "The Daily Show." Or that Stewart's guests -- when he's not chatting up Hollywood celebs about their new movies -- have included Bill Clinton, Bob Dole, former counterterrorism chief Richard Clarke, Bush adviser Karen Hughes and Republican National Committee Chairman Ed Gillespie. Stewart can tell sex jokes one minute and have a serious foreign policy discussion with Newsweek's Fareed Zakaria the next.

"When I listen to Jon, he really is profoundly concerned and angry about real issues," Koppel says. "He is to television news what a really great editorial cartoonist is to a newspaper." But, Koppel says, "a satirist gets to poke and prod and make fun of other people, and when you say, 'What about you, dummy?,' he says, 'I'm just a satirist.' "

CNN anchor Wolf Blitzer, who has interviewed Stewart and appeared on "The Daily Show," is another fan. "There's no doubt he's an important fact of life in this current political environment," Blitzer says. "Off camera, he's a very politically aware news junkie."

Jon Stuart Leibowitz, who grew up in suburban New Jersey, is a physicist's son who found himself tending bar and doing puppet shows for schoolchildren after graduating from Virginia's College of William and Mary. He dropped his last name when he started doing stand-up at Manhattan comedy clubs, waiting tables to get by.

Stewart landed gigs on MTV and Comedy Central and in 1993 wound up a finalist to replace David Letterman on NBC's "Late Night," losing out to Conan O'Brien. After his syndicated "Jon Stewart Show" was canceled after a single season, he popped up on programs such as "The Nanny" and HBO's "Larry Sanders Show."

When Stewart succeeded Craig Kilborn on "The Daily Show" in 1999, he transformed it into what Newsweek calls "the coolest pit stop on television." His program won Emmys this year and last. He will be profiled tomorrow on "60 Minutes."

"Even I'm sick of us," says Ben Karlin, the show's executive producer. But "the media beast must be fed," he added, amused that the show is being hyped by the "pack journalism" it regularly ridicules.

Stewart's humor is clearly fueled by anger. He's the guy at home "yelling at the TV," he says. Karlin say staffers come to morning meetings ticked off about various outrages and spend the day honing their insults into lighter material.

Stewart, who has called the Iraq war a mistake, is more likely than Jay Leno or David Letterman to ridicule Bush while going easy on Kerry, the Project for Excellence in Journalism found. "He's an outstanding comedian, but clearly he does comedy from the Democratic left perspective," says Republican strategist Mike Murphy. "A lot of people who watch Stewart and howl at the jokes already have their minds made up in the presidential race."

The secret of Stewart's appeal is that he mocks the conventions of journalism, with self-aggrandizing correspondents like Stephen Colbert and Rob Corddry standing in front of phony backdrops or making faces while interviewing unsuspecting citizens. In a sound-bite culture, Stewart uses video clips to highlight the absurdity of political spinners and media talking heads.

After playing a clip of Bush hitting Kerry on taxes by saying "the rich hire lawyers and accountants for a reason, to stick you with the tab," Stewart said, "Let me get this straight: Don't tax the rich because they'll get out if it? So your policy is, tax the hardworking people, because they're dumb-asses and they'll never figure it out?"

"Politics is funny, hilarious and stupid," says Jeff Jarvis, who oversees Conde Nast's online publications and maintains a blog called BuzzMachine.com. "But do you get that sense from networks and daily newspapers? Not really -- we get pompous about it. Stewart brings the humor back to it. He calls politicians bozos. And then he went over the next line on 'Crossfire' and called media guys bozos."

Stewart's Oct. 15 scolding of "Crossfire" co-hosts Tucker Carlson and Paul Begala -- and his calling Carlson a four-letter name -- was one of those weird, awkward, riveting television moments that more than 670,000 people downloaded from cnetnews.com in the following days. He said the program is "hurting America" by encouraging partisans to yell at each other.

Says Carlson: "Jon Stewart is a talented comedian, and all of a sudden he wants to be Kathleen Hall Jamieson," the University of Pennsylvania author and media analyst.

"There are things wrong with cable shout-shows, definitely. There are things wrong with 'Crossfire.' What bothered me was the pomposity and sanctimony, the notion that we're the problem. He doesn't understand the role of shows like ours in the media food chain. Not only was he not funny, he was not interesting. Banal."

Stewart is somewhat stunned by the reaction: "Imagine being criticized for going on 'Crossfire' and expressing an opinion, and it wasn't an opinion that held to the left-right roles they're accustomed to scripting. I'm far more comfortable in my role as comedian. It was only a moment of honest frustration. I probably should have been more delicate."

But he is fed up with a process in which "people who are giving talking points come on these shows and are questioned by people on the other talking-pointed side. 'Crossfire' is the crack cocaine, the purest distillation of it."

Some journalists have rallied to his defense. "Jon Stewart never said he was going to renounce his standing as a smart guy who went to William and Mary and as a sharp social critic," says NBC anchor Brian Williams, a past "Daily Show" guest. "Sure he has an impact. The din of our media has reached the point where we could use a have-you-no-sense-of-decency-sir-at-long-last moment."

Koppel takes issue with Stewart's insistence that journalists should put forth the "truth." "Jon feels people like me in particular should be more opinionated, not less. He feels I have a responsibility to get in there and tell the public, 'Look, this guy is lying' -- maybe not quite that blatantly. I disagree with that only in part. . . . In a live interview you can say, 'That doesn't sound right,' but you don't automatically have all the facts at your disposal."

Stewart, who is especially popular with the journalists he ridicules, disappointed some of them by joking his way through much of the Kerry interview. "Is it true that every time I use ketchup your wife gets a nickel?" he asked.

He offered this explanation to Fox's Bill O'Reilly: "I am very uncomfortable going more than a couple of minutes without a laugh because the same weakness that drove me into comedy also informs my show."

In a final absurdity, an Internet petition is urging Stewart to run for president.

"It's not that young people don't like politics," says Cox, of Wonkette.com. "The way politics is talked about in the media is alienating. They're seeing Jon Stewart as a kind of hero who will lead us out of the darkness." Of course, she adds, "that's not his job."

Howard Kurtz hosts CNN's weekly media program.

Jon Stewart says "The Daily Show" isn't pushing to change the political system: "We have a more selfish agenda, to entertain ourselves."

Jon Stewart has said he'll vote for Democratic presidential candidate John Kerry, who was on "The Daily Show" in August.