Olbermann finished the script shortly after 3 A.M. He e-mailed copies to his producers, and then he went to bed.

The jeremiad against Bush was a signature Olbermann effort, the sort of stylized, mocking tirade that has lately made him a cable-news sensation, the Edward R. Murrow of the Angry Left. Olbermann was pleased with the script, and the next day, before going on the air with it, he posted excerpts on the liberal blog Daily Kos, which is a fairly good representation of the Olbermann fan base. The Kossacks wholly approved. (“You excoriated the bloodyhanded, warmongering imbecile.” “This country cannot survive without you.” “Dude, you’ve got a pair of steel ones!” “I’m gonna print it out, hang it up and memorize it.”)

At MSNBC, the feedback was slightly more cautious. Olbermann’s original script identified the “cold-blooded killers” as everyone at the Pentagon and in the Bush Cabinet; when a colleague noted that that would include such relative moderates as Colin Powell and Defense Secretary Robert Gates, Olbermann modified the line. Phil Griffin, the senior vice-president in charge of MSNBC (“Phil thinks he’s my boss,” Olbermann says), raised the matter of tone. Why did Olbermann need to end his commentary by telling the President of the United States to “shut the hell up”?

“Because I can’t say, ‘Shut the fuck up,’ that’s why, frankly,” Olbermann responded. The line stayed in.

Phil Griffin is a compact, nearly bald man with the intensity and the revved-up metabolism of a TV-news field producer, which is how he spent his early career. He speaks in quick bursts, and his conversations tend to the elliptical. Griffin was Olbermann’s first television producer, nearly thirty years ago, when both of them were at the start of their careers, Griffin as a CNN producer, Olbermann as an innovative, eccentric radio sportscaster making his first foray into television. It was Griffin’s job to handle Olbermann, to teach him about the frenetic, video-hungry new world of cable news. In a way, he still sees himself as Olbermann’s handler. “You don’t take Keith on by just saying, ‘You can’t do that,’ ” Griffin told me. “Keith is reasonable. But you’ve got to be smart. Keith is usually two steps ahead of me, when I do come and say, ‘Keith . . .’ It’s a give-and-take.”

When, in 1981, Olbermann arrived at CNN, then still in its startup throes, he was, at twenty-two, seen as a sportscasting wunderkind—smart, offbeat, and possessed of an encyclopedic range of knowledge. He also had the reputation, even among those who admired his talents, of being somewhat difficult. Growing up in suburban Hastings-on-Hudson, in Westchester County, he was the sort of kid who, when his parents thought psychological testing was in order, responded to the Rorschach test by saying, “It looks like an inkblot.” Advised that Keith might be better served by a private education, his parents—Theodore, a commercial architect, and Marie, a preschool teacher—enrolled him at the Hackley School, in Tarrytown. It wasn’t an easy adjustment; Keith had skipped a grade and was younger than anyone else in his class, and he wasn’t a jock. But he was a good student, and the school’s radio station became his home. Olbermann worked as a sports stringer in college, at Cornell, and when he graduated, in 1979, he went directly to a sportscasting job at UPI radio in New York.

Olbermann’s style stood out from the start. He gently mocked the conventions of sportscasting (in his deep broadcaster’s timbre) even while observing them. At UPI, he became famous for drolly tallying the number of times athletes said “Y’know” during interviews. He also had a sometimes overbearing self-certainty. When he was twenty-three, he told Bill MacPhail, the former CBS Sports executive who had overseen the introduction of instant replay, that MacPhail didn’t know anything about television sports. In an argument with one of his supervisors at UPI, he so forcefully advocated his position (“God damn it, this is the minor leagues here,” he said, “and it’s things like this that are keeping us the minor leagues’’) that he was fired that afternoon. (The Wire Service Guild stepped in and saved his job.) His three-year career at CNN was, he says, “a continuing pitched battle.” He moved to a television station in Boston, and lasted a few months. At the age of twenty-five, he moved back home, a flameout, with few prospects. His agent sent his highlight tapes to stations around the country, but most station managers didn’t quite know what to make of him. “The standard response,” he says, “was ‘I like him, but is Baltimore ready for him?’ ”

Jeff Wald, who was then the news director of KTLA Channel 5, in Los Angeles, had heard the stories, but he saw Olbermann’s tapes, and was curious. “I just said, ‘He’s the guy,’ ” Wald recalls. “Regardless of the baggage he may or may not have, I want to meet this guy and see if he’s the real deal. And he was.”

Wald wanted someone unusual, and he got it. For one thing, Olbermann almost certainly was the only television sportscaster in Los Angeles who didn’t drive. Olbermann, who is six feet three and a half, once bumped his head while leaping into a subway car; it permanently upset his equilibrium, which makes driving a trial. (He says he loses depth perception at speeds greater than fifteen miles per hour.) He also hates flying, and that made it difficult to follow the local teams, but it was just as well; Olbermann firmly resisted the chumminess that often develops between sports journalists and their subjects. Wald says that the only argument he had with Olbermann came when Olbermann refused an assignment to cover spring training. “He thought that was going to compromise his objectivity and reporting,” Wald recalls. “I didn’t know at the time that he didn’t like to fly, but I think that he was probably right in his reasons.”

In 1992, Olbermann joined ESPN, where his erudite, wise-guy style flowered into an artful, full-blown satire of the cliché-ridden form: “That’s a six-four-three double play if you’re scoring at home. Or if you’re by yourself.”

Olbermann’s tenure at ESPN was characteristically contentious. One of his co-anchors, Suzy Kolber, has said that Olbermann was sometimes so overbearing that she would lock herself in the bathroom and cry. Another colleague, Mike Soltys, has said that when Olbermann left the network, in 1997, “he didn’t burn bridges here—he napalmed them.”

Olbermann was glad enough to be leaving the grind of full-time sportscasting behind. His new job brought him out of the toy department and into the news side of broadcasting, with a show on NBC’s new cable-news channel, MSNBC. The producer of the broadcast, called “The Big Show,” was Phil Griffin, who was delighted to be working with Olbermann again. But in 1998, when the news cycle was hijacked by the Monica Lewinsky scandal, Olbermann found himself the anchor of a nightly newscast called “White House in Crisis.” He grew so weary of the story that getting him on the air every day became a battle. “Keith just didn’t want to go there,” Griffin recalls. “He didn’t want to do the story, and it evolved into the hottest story of the time. It made my life miserable. It was bad. And it did not end pretty.”

Once again, Olbermann left a job unhappily, returning to sportscasting at Fox Sports. He was subsequently fired, and the remainder of his contract was paid off. (“I fired him,” Rupert Murdoch said recently. “He’s crazy.”)

But Phil Griffin continued to admire Olbermann’s on-air talents, and helped to bring him back to MSNBC in 2003, to do a new show called “Countdown.” Shortly afterward, Griffin ran into an old colleague at CNN, who told him that that network had considered hiring Olbermann, but focus-group tests showed that audiences didn’t like him. “I can honestly tell you it shook me up a little bit,” Griffin recalls. “But we knew what we were getting.” He added, “I’ve known Keith for twenty-seven years. CNN. First day he was in TV, I knew right away that Keith had something that I’d never seen. He was made for this. I mean, the guy is crazy, but he is made for this.”

Olbermann chose his office, a corner office on the fourth floor of NBC’s Rockefeller Plaza headquarters, for its view. From his desk, he can look out the window and see, directly across Sixth Avenue, the studios of Fox News, the broadcast home of his rival Bill O’Reilly. “Sometimes I imagine that I hear a howl coming from there,” Olbermann told me during a visit one afternoon. “I have been accused of having an obsession with him. I am a minor-leaguer compared to his obsession with me.”

The Olbermann-O’Reilly feud, which is wholly Olbermann’s creation, began with a wisecrack in 2003, the first year of “Countdown.” It evolved after Olbermann instituted a farcical segment called “The Worst Person in the World,” in which O’Reilly, depicted as a pompous buffoon, was regularly cited. O’Reilly, the biggest draw of the highest-rated cable-news network, could only lose by engaging with Olbermann, but he could not resist. Refusing to mention Olbermann by name, he sponsored a petition drive to have him replaced, and eventually began to aim on-air broadsides against NBC’s parent company, General Electric, and its chairman, Jeffrey Immelt. “If my child were killed in Iraq, I would blame the likes of Jeffrey Immelt,” O’Reilly asserted in April, citing G.E.’s business relationship with Iran. (The company began phasing out its contracts there in 2005.) This only encouraged Olbermann, who subjected Bill-O (as Olbermann calls him) to near-daily barrages of acid caricature. Instead of using video clips of O’Reilly for his routines, Olbermann began voicing O’Reilly’s words himself, in a demonic mimicry of the Ted Baxter character on “The Mary Tyler Moore Show.”

When “Countdown” was still new, in 2004, Rick Kaplan, then the president of MSNBC, told Olbermann that he wanted the program to be the cable network’s “newscast of record.” Largely owing to the license that Olbermann took in his on-air duelling with O’Reilly, it has become more like a nightly political insult-comedy routine. Olbermann’s Fox-bashing struck a chord with a core audience deeply sympathetic to the view that the conservative-leaning Fox News (“Fox Noise,” Olbermann calls it) has degraded journalism “in the same sense that George Bush lowered and made even more disreputable the Presidency of the United States.”

“Bill O’Reilly made Keith Olbermann,” Phil Griffin says. Olbermann concurs, saying, “I really do owe him a percentage of my salary.”

The O’Reilly feud was the gateway to Olbermann’s emergence as a political polemicist. It was a short leap from denigrating Bill-O to Olbermann’s first “Special Comment,” aimed at then Secretary of Defense Donald Rumsfeld, in August, 2006. While waiting out a flight delay in Los Angeles, Olbermann read the highlights of a speech that Rumsfeld had just delivered to the American Legion, in which he charged that some critics of the Administration’s war plan suffered “moral or intellectual confusion about what is right or wrong.” Downing “a couple of screwdrivers,” Olbermann says, he wrote a rebuke of the Defense Secretary, which he read on the air the next day. “The man who sees absolutes where all other men see nuances and shades of meaning is either a prophet or a quack,” he began. “Donald H. Rumsfeld is not a prophet.” Olbermann went on to lecture Rumsfeld about the workings of a democracy and the nature of fascism, and concluded by quoting from Edward R. Murrow’s 1954 denunciation of Joseph McCarthy and McCarthyism. He says that he didn’t know how the commentary would play, with the NBC brass or with the audience. “I really did think, Well, if this is the end of my career, I will have gone down for a good cause.”

His bosses loved it. “I think we’re onto something,” the president of NBC News, Steve Capus, told me. “That’s what we keep hearing from the audience, more and more, is that they appreciate that we have people who are actually speaking truth to power, or being transparent in their own personal viewpoints.” That’s another way of saying that liberals, after many failed attempts, seem finally to have found their own Bill O’Reilly. Fox News still dominates the cable competition, and MSNBC over all continues to lag behind second-place CNN. O’Reilly’s audience is more than twice as big as Olbermann’s, which airs in the same prime-time period. But Olbermann’s ratings grew by nearly seventy-five per cent the year he began doing Special Comments, and the show is making money, a rare hit in MSNBC’s twelve-year run. “All of a sudden, he took off,” Griffin says. “In ways that MSNBC never had a show take off.”

Olbermann’s success, like O’Reilly’s, is evidence of viewer cocooning—the inclination to seek out programming that reinforces one’s own firmly held political views. “People want to identify,” Griffin says. “They want the shortcut. ‘Wow, that guy’s smart. I get him.’ In this crazy world of so much information, you look for places where you identify, or you see where you fit into the spectrum, because you get all this information all day long.”

Capus and Griffin insist that Olbermann’s broadcast is like an opinion section in a newspaper, suitable to what they call MSNBC’s “cable sensibility.” Olbermann differs. He begins each “Countdown” with the Beethoven theme from NBC’s “Huntley-Brinkley Report,” and concludes with Murrow’s signature sign-off, “Good night, and good luck.” He maintains that “Countdown” is very much part of that continuum. “It is a newscast with commentary and analysis, the way most really good newscasts used to be,” he says. “Dosages of the various components vary in a greater degree than we’re used to, or maybe were even done in the heyday of this kind of thing. But if you listen to those daily Murrow newscasts in the forties on the radio, Murrow would do the news, two and a half, three minutes, take a break, and then do a two- or three-minute commentary.” It could be argued that Murrow’s work in wartime London—he would report on the Battle of Britain, and also advocate against continued American neutrality in the war—is hardly the same thing as telling the President to “shut the hell up,’’ or posing the question regarding Bush (as Olbermann did): “Pathological Presidential Liar or an Idiot-in-Chief?”

But Olbermann contends that the labored pretense of neutrality in the news business is a fruitless exercise. “There are people who, with absolute conviction, believe that Brian Williams is a Communist,” he said. “There are people who, with absolute conviction, believe that Katie Couric is in the pay of the Pentagon. There are people who are absolutely certain that Charlie Gibson sleeps with Hillary Clinton, based on the last debate. This is an old schoolyard thing I learned from being repeatedly beat up in the fourth grade. It finally dawned on me one day—they are going to keep beating me up whether I respond to them or not.” Olbermann continued, “Brian sometimes looks like his collar button is going to burst from the restraint that he has. I know the pain that he goes through; he measures each word like an apothecary—and they beat him up, too. The point is, why not? Why not add something to the discourse?”