VOX FOX.(Fox News CEO Roger Ailes)

One morning not long ago, the co-hosts of "Fox & Friends,"the Fox News network's raucous and right-leaning version of the "Today"show, were promoting Fox-branded merchandise such as baseball caps and soap-on-a-rope when Steve Doocy, a co-anchor, turned to his partner, E. D. Hill, and said, "You know who's really jealous about our merchandising?"Doocy, who doubles as the weatherman, answered his own question: "My dentist is so jealous. You've seen him on TV--Aaron Brown. You know, the guy on CNN--he does that show at night? He just works nights over there. But during the day he's our dentist. Do we have a picture?”

Up popped a grim photograph of CNN's principal nighttime anchor, Aaron Brown. "That man looks just like a dentist, doesn't he?"Doocy said, and soon he and Hill were chatting about whether Brown was a good dentist and what he charged for a cleaning. Brown's picture lingered on the screen for a full minute, over bold, block-lettered captions: "aaron brown dds,” followed by "molar man,” followed by "arrogant brown.”

That bit of intramural japery, which aired on December 13, 2001, was choreographed by Roger Ailes, the chairman and C.E.O. of the sometimes raucous and right-leaning Fox News. Ailes was trying to strike back at Brown for publicly "putting us down,"he says. "I don't ignore anything. Somebody gets in my face, I get in their face."Ailes requires enemies the way a tank requires fuel, and as he contemplated retaliation he kept thinking, I know someone who looks like Aaron Brown. Then it came to him. He telephoned Doocy, telling him, "Steve, just say that Aaron's your dentist. Then have your co-anchor say, 'He's not a dentist. He's on CNN!' "Ailes, a man of Falstaffian girth, roared with laughter, and continued, "I said, 'Doocy, no matter what happens, even if they torture you, say he's your dentist!' "For two days, Doocy followed this script, and for two days, Ailes recalled fondly, "I'm sitting here laughing my ass off."

Aaron Brown, for his part, was not laughing his ass off. "I thought it was sort of juvenile,"he said. "This is a little game they play. It's Roger's game. Roger seeks to define his political or journalistic opponents and destroy them."

There have been many such memories for Ailes, some playful, some brutal, all purposeful. In March, when antiwar protesters blocked traffic on Fifth Avenue and paraded in front of the Fox News offices on Sixth Avenue between Forty-seventh and Forty-eighth Streets, the electronic news ticker that wraps around the building suspended Iraq-war headlines to respond: "attention protesters: the michael moore fan club meets thursday at a phone booth at sixth avenue and 50th street."Marvin Himelfarb, a former sitcom writer, wrote the ticker copy, but Ailes was his happy abettor. Of the announcements, Ailes says, "I helped with a couple."Paula Zahn recalls that when she told Ailes she was moving to CNN in 2001, "he made it very clear to me that he was not going to make life easy for me. He told me I was allowing myself to be drawn into what he called a holy war between CNN and Fox News, and that I was going to have to pay a price for that."(Ailes brought a lawsuit charging that Zahn's agent interfered with Fox's contract; it was dismissed by two state courts.) Subsequently, "Fox & Friends"disparaged Zahn, whose "American Morning"aired at the same time. Mancow Muller, the Chicago-based radio shock jock who appears regularly on the morning show, said of Zahn--screamed, actually--"I kick your ass, Paula! You take on us, we'll kill you, Paula! We'll kill you! We will kill you, Paula!"Walter Isaacson, who was then CNN chairman, acknowledges that Ailes's approach "constrains your action. You wake up aware of Roger. He's always on the attack."Ailes doesn't deny that he tries to intimidate people: "I'd say half of it is because people let their heads be played with and half of it is just my sense of humor."

Ailes is sixty-three and does not look immediately fearsome. He says he is five feet nine inches tall and weighs two hundred and twenty-five pounds; his jowls droop over his collar. With his pallor and barely perceptible eyebrows, Ailes looks like someone who has spent a lifetime under fluorescent lights. In many ways, he is a throwback--to the fifties, perhaps. He slathers a morning bagel with butter and cream cheese; he often wears white shirts with French cuffs and a tie clip. Nine years ago, on the Don Imus radio program, he referred to Mary Matalin and Jane Wallace, then the co-hosts of a CNBC show, as "girls who, if you went into a bar around seven, you wouldn't pay a lot of attention, but get to be 10s around closing time.”

Roger Ailes is also a television pioneer, someone who had no background in news and yet created something different in the TV news business. In large part because of Ailes, Fox News, in its short life--it d?buted on October 7, 1996--has established an unmistakable identity: it is opinionated and conservative, and its news is delivered by people who themselves are often unabashedly opinionated and conservative. When Ted Turner launched the Cable News Network in 1980, CNN took the idea of all-news radio and transferred it to television. The Fox News idea was to make another sort of transition: to bring the heated, sometimes confrontational atmosphere of talk radio into the television studio.