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As a fan, a viewer, a consciousness-on-a-couch, I had drifted away, years ago, from the Ultimate Fighting Championship. Had I aged out of it, maybe—lost my youthful tolerance for violence? Softer midriff, softer mind? At any rate, it seemed to be over between me and the UFC. Until last year, that is, when I was goosed in my psyche by the fighter-phenomenon Conor “The Notorious” McGregor. Peacocking around in his beautiful suits, lightly promising destruction to his enemies, he zapped through my middle-aged culture filters. He was unbeaten in the UFC. His left fist was an astonishment. On iTunes, I bought his 2013 fight against Max Holloway: There’s McGregor, dazzling with witty hook kicks and punches from the future, the bruises slowly thickening Holloway’s face like an index of stupefaction. “Let’s put him away,” advises John Kavanagh, McGregor’s coach and cornerman, icing him down between the second and third rounds. “More water?” “Yeah, a little bit,” shrugs easy-breathing McGregor. “I feel great.” “You look beautiful,” chuckles Kavanagh. “You look beautiful, man.” I was in love.

The UFC is the largest and most dynamic promotion company in the still-emergent sport of mixed martial arts (MMA), and Conor McGregor, 27, a former plumber’s apprentice from Dublin, is its most resplendently entertaining—and bankable—character. Inside the Octagon, the eight-sided, chain-link-fenced UFC ring, he cuts a figure of near-comic bellicosity, hoisting his fists and bending his knees like a Regency pugilist; outside of it he sells the fights like nobody else. He appeared on the March 2016 cover of Fighters Only magazine in a pink bow tie. In his chewy Dublin accent, he methodically maddens his opponents. And he wins and he wins. In December he fought Jose Aldo for the UFC featherweight belt, and the effects of the McGregor hype-out were startlingly visible: Aldo is a fearsome and seasoned fighter, but climbing into the Octagon he was skittish, cramped, out of focus. He was pre-beaten, and after 13 seconds of bouncing, unbearable anxiety, he walked with what looked like relief into the good night of McGregor’s left hand.

So in early March I flew to Las Vegas to see McGregor (then 7–0 in the UFC) fight Nate Diaz at UFC 196—that is, the 196th major event staged by the company. It was primary season in America, right between the 11th and 12th Republican debates, and as turbulence spanked the plane and the tray tables rattled, it occurred to me that we might have flown into a stray pocket of Trumpian oratory, Trump-breath, a little verbal chaos-cloud unmoored from its source and drifting hazardously at 32,000 feet. Hot air surrounded the fight, too—most of it McGregor’s. “I’m certainly going to toy with the young boy,” he said of Diaz (three years his senior) at the prefight press conferences. “I’m going to play with him.” He ungallantly mocked Diaz for his work teaching jiu-jitsu to kids—“He makes gang signs with the right hand and animal balloons with the left hand!”—and then, more Tyson-esquely, promised to eat Diaz’s carcass in front of his “little gazelle friends.” Diaz, rhetorically overmatched, sensibly confined himself to some villainous scowling and swearing.

You probably didn’t read about McGregor-Diaz—or about Holm-Tate, the equally sensational women’s MMA bout immediately beneath it on the bill at UFC 196—in the sports section of your Sunday paper. And yet there were 15,000 howling fans at the MGM Grand and some 1.5 million pay-per-view buys at $49.99 a pop or more. That’s the UFC in 2016: ubiquitous, but not fully visible, like tattoos, or Paxil. It’s come a long way from its circus-of-violence origins. At the promotion’s maiden event—UFC 1, in 1993—boxers fought grapplers, sumo guys fought karate wizards, and gorillas fought octopuses. Okay, not the last part. But it was cartoonish and impure and very, very brutal.

Thus inspired, people, fighters, maniacs began mixing it all up, and competition-level MMA entered a new phase. Blood flowed, unregulated. Joe Rogan, the versatile stand-up comedian who also works as a UFC commentator, has talked about the days when telling people you were associated with the UFC was like telling them you were in the porn industry. Slowly, out of the primordial blitzing and gouging, rules emerged. No head kicks to a downed opponent. No hair-pulling or groin strikes. Small padded gloves were introduced. Today, every UFC event should by rights begin with a short, hats-off-please-gentlemen prayer of thanks to Blessed John McCain, who famously decried MMA as “human cockfighting” and whose senatorial intervention in the late ’90s—when he persuaded 36 states to ban it from cable TV—obliged the UFC to clean up its act, thereby setting it on the road to mass appeal. Since the early 2000s, the sport has consciously counterbranded itself against the larger, less organized, and slower-moving boxing industry: The UFC, with its near-monopoly on MMA, can crisply and dramatically give the fans the fights they want.

MMA today is a technical and highly evolved sport, and fans arriving at a UFC event have a coherent set of expectations. The mingling of the martial arts having multiplied the ways in which you can be rendered unconscious—by punch, kick, elbow jab, knee strike, or arm across the carotid artery (the “rear naked choke”)—fighters generally proceed with great wariness. Of the three five-minute rounds in a standard MMA bout, two and a half can pass in a kind of supercharged inertia: The fighters bob and feint, each waiting for his opponent to commit himself, and beneath desultory cries of “Hit him!” you can hear the sizzle as force fields of vigilance collide and separate inside the Octagon. But for long stretches nothing happens. This is why an explosive, all-action knockout artist like McGregor is so valuable to the UFC. He makes things happen.

The initial hype for UFC 196 was that McGregor was going up a weight class—from featherweight (145 pounds) to lightweight (155 pounds)—to fight the lightweight champion Rafael dos Anjos. If he beat dos Anjos, in other words (and for McGregor there was naturally no if about it), he would hold two belts and rule two divisions. But dos Anjos broke his foot in training two weeks before the fight, and his last-minute replacement was Diaz, a brooding, slightly out-of-condition 170-pound welterweight from Stockton, California. So here was Conor McGregor, the fighting metrosexual, flamboyant flattener of dangerous little men, abruptly vaulting up two weight classes and chancing his reputation and his record on what was no longer even a title fight. Bang the gong of hubris! Hail the volatility of the UFC!

Nate Diaz moves like a brawler inside a sensei inside a spider inside a teenager. His self-promotion is minimal, almost inverted, but once he enters the Octagon he shows a lively interest in mental supremacy and poor sportsmanship: He likes to slap his opponents, drop his guard and taunt them, and flourish his middle finger in their faces. He cuts easily and bleeds copiously. His jiu-jitsu is strong, as is his boxing. And for UFC 196 he played—beautifully—the scarred and skulking outsider to McGregor’s golden boy.

The crowd that night in the MGM Grand was moody, bloodthirsty, intoxicated, tribal, diabolically fickle—which is to say, typical. A crowd from the dawn of time. And as McGregor’s walk-out music, the spooky, wind-under-the-door croon of Sinéad O’Connor singing “The Foggy Dew,” floated through the arena—As down the glen one Easter morn / To a city fair rode I—the Irishmen in the place filled their lungs and roared. There he was, burrowing out of the tunnel with his entourage: buoyant, smiling, mantled in the Irish tricolor. He would make his millions. He would claim this victory for his people. He would freeze the gormless Diaz inside an enchanted sphere of whirling feet and stinging dandy’s fists. And then he would drop him with that monster left.

Except he didn’t. To get a sense of the predicament of Conor McGregor as the fight moved into its second round, take the following two quotes—“Reality was giving its lesson, its mishmash of scripture and physics” (Ted Hughes), and “Reality is that which, when you stop believing in it, doesn’t go away” (Philip K. Dick)—and for the word reality substitute the words Nate Diaz. Predictably covered in blood, Diaz remained undevastated by McGregor’s punching power, and quite unaffected by his charm—unmagicked, as it were, by the foggy dew. Gristly, obdurate, irreducible, Diaz was still there. McGregor, meanwhile, his whole game having coagulated around that huge repetitive left, was slowing down. Diaz was coming forward, heavily, to chants of “Di-az! Di-az!” from the turning crowd. And he was landing shots. After some of them McGregor would nervously lick his lips, as if offended by the taste. Then a right-left combination dazed him, staggered him, and Diaz—fully himself at last—dropped his hands and gave McGregor a gory, gum-shield-distorted grin. The middle finger was surely coming. McGregor went for a takedown, scrambling to embrace Diaz’s legs. It was a kind of surrender. Diaz, awkward customer turned nemesis, got on top of McGregor and swiftly and expertly worked an arm under his chin, and there ended the lesson: Pride goeth before a rear naked choke.

McGregor-Diaz was not the only shock reversal at UFC 196. The much-loved Holly Holm, defending her bantamweight belt in the women’s division, was rear-naked-choked by Miesha Tate. (Although Holm, unlike McGregor, did not tap out as the choke sank in—she went to sleep punching, her fists groggily flailing the air until her brain cut the power.) Two stars, dimmed or dented. Two brand ambassadors, horizontal. In the event’s aftermath, as a backwash of depressed Irishry sloshed around the MGM Grand, the question arose: Had the UFC blown it, lost money, in its pursuit of the spectacular? To which the only possible answer is: Who cares? Holly Holm, beautiful Holly Holm, literally went out swinging. The light in Nate Diaz’s eyes as he reared up, wearing his upside-down crown of blood, from the prone and tapped-out form of Conor McGregor—it was miles away, worlds away. It was Homeric.

UFC 200 looms, in July, heralded by the now-familiar chaos: A McGregor-Diaz rematch was the main event, until McGregor convulsed the Internet on April 19 by announcing his retirement on Twitter. Two days later he unretired on Facebook, but the UFC had already dropped him from the bill. It’s moving fast, this stuff. Turn away and you’ll miss it.

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