Martin Kaymer shoots a 65 for the second consecutive day Friday, setting a record for a 36-hole low at the U.S. Open. (David Cannon/Getty Images)

Three years ago, Martin Kaymer ground his way through the first two rounds of the U.S. Open at Congressional Country Club, unable to break par, making the cut by a shot. He finished and looked aghast at the leader board. Rory McIlroy sat atop the field, six shots better than anyone else, a full 13 shots better than Kaymer.

“I thought, ‘I mean, how can you shoot that low?’ ” Kaymer said. “And that’s probably what a lot of other people think about me right now.”

What the rest of the U.S. Open field thinks of Kaymer must be a combination of wonderment and frustration. For the second straight day at Pinehurst No. 2, where birdies are supposed to be as scarce as unsweetened tea, Kaymer simply played a different brand of golf. He shot his second consecutive 65 on a course that had not previously allowed such a low score in an Open, and he sits at 10-under-par 130 — beating McIlroy’s record for low 36-hole total in the Open by one and tying the mark for the best score at the midway mark of any major.

“It gets boring, the words that I use,” Kaymer said. “But I mean, there’s not much to say. It’s just good right now the way I play golf.”

So, yawn, end the story — and the tournament — right there? Well, not quite. There is much to admire in Kaymer’s display over the past two days: That of the 1,257 bogeys made by the field, he made just one. That his total matched the 66-64 posted by Nick Faldo at the 1992 British Open as the best through the first two rounds of a major. That when he started to tire and even fiddle with what might have been ailing wrists over his final four holes, he got up-and-down from three straight bunkers.

“He’s dialed in,” said Keegan Bradley, who played with Kaymer, managed back-to-back 69s — and still trails by eight. “He’s as dialed in as I’ve ever seen.”

Kaymer is German and plays with the very symbol of engineering precision, the Mercedes-Benz logo, on the breast of his shirt. Yet no player is beyond stumbling at a U.S. Open. There are, of course, those in chase — Brendon Todd of nearby Cary, N.C., who shot 67 on Friday and is 4 under, along with Kevin Na and Brandt Snedeker, a shot further back.

Plus, there is the burden few others have had: protecting such a lead. Kaymer’s six-shot advantage heading into the final two rounds ties the U.S. Open mark set by Tiger Woods in 2000 and matched by McIlroy in 2011.

“If I was Martin, hopefully I’d be thinking about how to get seven ahead and then how to get eight ahead and then how to get nine ahead,” McIlroy said. “Especially on a golf course like this, you can’t go out trying to protect anything. You just got to keep your foot to the floor and just keep it going.”

Which, Kaymer said, is his intent. But before the weekend arrives, there are three events with which to compare the past two days: McIlroy’s command performance at Congressional in 2011 and the two previous U.S. Opens held at Pinehurst.

McIlroy’s dismantling of rain-softened Congressional made the Open feel like the St. Jude Classic. He became the fastest player to get to 10 under in the Open, needing just 26 holes. (It took Kaymer 32, so he is just second fastest.) Because Congressional played to a par 71, he was 11 under at the midway point en route to posting a 16-under total — both Open records, though Kaymer beat his total score by a shot.

“I think what Martin’s doing is more impressive than what I did at Congressional just because of how difficult the golf course is,” McIlroy said. “There’s trouble lying at every corner, at any missed green. Congressional was a little more benign than this is, a little softer, a little more receptive.”

What can’t be known: Will Kaymer follow it up as McIlroy did? McIlroy responded with rounds of 68 and 69 and sauntered to an eight-shot victory. The field agrees on one thing: The result of this affair is largely up to Kaymer.

“If he does it for two more days, then we’re all playing for second spot,” said Adam Scott, the world’s top-ranked player. “But we all know that U.S. Opens get very difficult.”

That would describe the other Opens here, too. In 1999, David Duval, Phil Mickelson and Payne Stewart shared the 36-hole lead at 3 under, and Stewart’s winning par putt on the 18th green Sunday — a moment memorialized in a statue here — gave him a 72-hole total of 1-under 279. In 2005, Olin Browne, Jason Gore and Retief Goosen held the lead at 2 under, but by Sunday, Michael Campbell’s even-par 280 was good enough to beat Tiger Woods by two.

So Pinehurst No. 2 has never produced anything like this — a blowout, at least for now. It has, too, never hosted a leader as confident and comfortable with himself, his game, the course and the surroundings as Kaymer was over these first two days.

“I look at the scoreboards; it’s enjoyable,” Kaymer said. “To see what’s going on, to watch yourself, how you react, if you’re leading by five, by six.”

Yet before he left the grounds Friday night, Snedeker uttered one truism: “No lead is safe in a U.S. Open.” Over the next two days, it will be up to Kaymer to counter that.