South African cards solid round as big names Kaymer, Donald and Westwood struggle on a rainy day at Congressional.
Mind control is the major factor for Louis Oosthuizen
Leading a major championship and winning a major championship have proved to be very different things in recent times.
Whoever is out in front in the US Open at Congressional on Saturday night will find little comfort in what has happened the past two years. Of the last eight 54-hole leaders only one - Louis Oosthuizen at St Andrews last July- has gone on to triumph.
All around the South African, who turned a four-shot advantage into an amazing seven-stroke British Open victory, are the battered and bruised bodies of others who came to grief.
Most vivid in the memory, of course, is Rory McIlroy, who from four clear at the Masters in April collapsed to an 80 and all the way to 15th place a massive 10 strokes behind Charl Schwartzel.
But he is far from alone in suffering such a meltdown.
At the US Open and US PGA last year the Americans Dustin Johnson and Nick Watney were three ahead, but shot 82 and 81 respectively.
Johnson finished eighth five adrift of Graeme McDowell, Watney 18th seven behind Martin Kaymer.
Before them it was Lee Westwood, overtaken by Phil Mickelson at Augusta, and before him Tiger Woods, who after 14 majors won from the front saw Korean YE Yang incredibly come from two behind to win the PGA title by three.
Woods shot 75, Westwood 71, while at Turnberry in the 2009 Open the 72 of 59-year-old Tom Watson was not quite good enough to make him golf's oldest major champion by an unbelievable 11 years.
Stewart Cink fired a 69 and beat the five-time winner in a play-off.
Ricky Barnes led the 2009 US Open by one with a round to go, but his 76 opened the door for Lucas Glover.
So how did Oosthuizen do it when other far bigger names could not?
"I was very confident the way I played," he said. "I was never scared on any shot and there was no particular hole that I felt scared of and I was driving it so well.
"At St Andrews everything is off the tee. If you can place it in a fairway all the time, missing all the bunkers, you've already won most of it.
"So that helped a lot. And it didn't feel like on the Sunday anyone really pushed me.
"I think the Friday night was probably the worst for me because I had 27 hours, I think, before my next tee time.
"But the way I finished on the Saturday, finishing two or three under the last five holes just gave me a bit of confidence going into the next day."
Asked what was the most important thing mentally he added: "The way I stayed in the present - I never for one minute thought of winning the tournament during the round."
Never for one full minute maybe, but certainly for a few seconds.
"It was so difficult the last six holes because with a seven-shot lead all of a sudden you're thinking of standing with the Claret Jug.
"You've got to get yourself out of that mind frame and think shot for shot. Only after my second shot on 17 did I feel like I'm not going to throw it away from here."
Yang had a three-under 68 comprising five birdies and two bogeys yesterday. "I think the course setup is a bit more to my advantage than the other previous US Opens," he said.
"And also I've been playing a lot more conservatively this week and practiced a lot, played less bonehead plays. So I think overall the course and my conservative approach is helpful."
Oosthuizen carded a two-under 69. "I'm happy with my score," Oosthuizen said. "I made four bogeys, but on this golf course it's got a lot of bogeys out there.
"But today there was a lot of birdies, as well. So it's just a matter of trying to get as many pars on your card, because then you've at least got opportunities for birdies."
Among a large group tied on one-under 70 was Graeme McDowell, the defending champion. He opened with a bogey, but was at one under by the turn and parred his way down the back nine.
"I felt really, good this morning. I felt normal," said McDowell.
World Nos 1 and 3, Luke Donald and Martin Kaymer, both struggled to an opening 74, while Lee Westwood, the world No 2, faired even worse, carding a four-over 75.