As Rory McIlroy made a double bogey on the 18th hole at Congressional Country Club on Friday, the same thought raced through thousands of minds. You could hear it in the gasps of disappointment and the “oh, nos” as his second shot splashed in the pond.

Is the slim 22-year-old, who has shot 65-66 — 11-under-par 131 so far — about to crash and crumble on the weekend at the U.S. Open, blowing a six-shot lead with 36 holes to play, just as he squandered a four-shot margin on Sunday at the Masters when he shot a slump-shouldered, lost-boy-looking 80?

Or is he about to grow before our eyes, take the next step toward a greatness that seems within his grasp and not only win this Open but smash some of Tiger Woods’s most “unbreakable” records in the process? Will this Open be remembered as the one when Woods pulled out and McIlroy pushed through, playing as spectacularly as Tiger ever did at his best?

In making up your mind, here’s a little help from Brandt Snedeker, ranked 46th in the world: “He’s probably got more talent in his pinkie than I have in my whole body. He is unbelievably talented. . . .I love watching him play because it’s a very classical, beautiful golf swing. He’s only going to get harder to beat. It’s fun to kind of watch him grow up.”

That is a summary of the 111th U.S. Open: Watching him grow up. And in golf right now, after his 63 to start the 2010 British Open, after his 65 to begin the 2011 Masters, on top of his No. 8 ranking in the world and his annihilation of the competition so far in this Open, the only “him” in golf right now is McIlroy.

“Anybody who makes people want to tune in and watch is a great ambassador, and Rory McIlroy makes people want to do that,” Snedecker added. “He’s got a great head on his shoulders, which is very hard to do with the amount of success he’s had at such a young age. You couldn’t ask for a better kid to be out there representing the game.”

So, take the challenge. Even McIlroy can’t know how this story turns out. “I’m feeling good, feeling very good, you know,” he said, laughing, after missing only four greens in regulation in two days. “It’s funny to me. It feels quite simple. . . . I really don’t know what to say. I put myself in great position. But I know more than probably anyone else what can happen. So I’ve got to stay really focused and try and finish this thing off.”

Without doubt, McIlroy’s walk off the 18th green Friday looked far too much like his demeanor and posture on the back nine at Augusta: hangdog, humbled, suddenly young. It should be said, because he is acutely conscious this is part of the problem he must solve.

After the Masters, McIlroy mulled, consulted, even talked with Jack Nicklaus, about what lessons to learn. The message came through clear. “I needed to be a little more arrogant. . . [but] just on the golf course,” he said. “Have a bit of an attitude, you know?”

Doesn’t that come from being a working-class Northern Irishman whose dad took three jobs to subsidize his golf career? Doesn’t that come with curly hair, a mischievous eye and that gorgeous snap to a high, full finish that makes his golf swing look impossibly perfect? Apparently not. Modest kid, kind heart. But he’s getting over it.

My own view is unalloyed: McIlroy wins this Open. He blows up Tiger’s record winning score of 12 under par. And, if second-place Y.E. Yang stumbles just a bit, McIlroy will take a run at Woods’s almost unbelievable winning margin of 15 strokes.

Why? In part because McIlroy seems like part of the next generation that grew up on Tiger, but thinks it’s time for him to be surpassed. In the gallery beside the 18th hole, Sam Lee, Patrick Moriarty and Charles Kemper were quite sure what was transpiring in front of them. “We are watching history,” Lee said.

“He’s going to break Tiger’s [Open] record,” Moriarty said.

“McIlroy’s playing with [Phil] Mickelson, who is twice his age,” Kemper said. “And Rory is just out there destroying him.”

This trio of Rockville High athletes found the game through Woods, but recognizes McIlroy as the next evolution — their wave. Lee, 17, has shot a 71, Moriarty, 15, a 72, and Kemper, a baseball player, says it’s now the rule that excellent teenage athletes play golf even if they aren’t on the golf team like Lee and Moriarty. They know 13-year-olds who challenge par on local courses.

Golf has a lovely way of jumping and linking generations. As the three teens were talking, 65-year-old Joe Malloy of Alexandria just walked up and joined the conversation, telling how he saw the U.S. Open playoff at Merion in 1971, when Lee Trevino tossed a toy snake at Nicklaus’s feet on the first tee, rattling the Bear with his innocent joke. How far did Nicklaus really hit the ball with steel shafts and wooden club heads, the kids wonder? About 280, maybe? In a long-drive contest in 1964, 341 yards, 17 inches. Dude, for real!?

Old times and new blend, as they always do in golf. The years fly past. Trevino tosses his rattler at Jack. Tom Watson takes Jack’s throne. Finally, after dry years, Tiger arrives, reigns for a dozen years. It’s time again. You can feel it. Is it McIlroy?

“You can’t win without losing first,” Moriarty said. “Rory just had to learn.”

The unthinkable happens fast. You watch it with your own eyes, but hesitate to say the obvious. But there it is, bright as a June sun. It will take a decade, at the least, to measure McIlroy’s career, or anybody’s against Woods. But Tiger’s most breathtaking one-week masterpiece of 11 years ago is under ferocious attack right now.

Lowest 36-hole score in U.S. Open history — in the books. First man to reach 13 under par in the U.S. Open — McIlroy did it, for one hole, after he birdied the 17th Friday.

Don’t say just a runaway. We’re watching history and probably of the very happiest kind.