Ricky Barnes scratched out an even-par 70 and kept his one-shot lead over Lucas Glover.
It was the final hour of the rain-delayed third round that suddenly raised so many intriguing possibilities.
Barnes, who has never held a 54-hole lead anywhere but the minor leagues, was at 8-under 202 and paired in the final group with Glover, who rallied with three birdies on the back nine to shoot 70.
I knew it was going to be wet and tough, and I knew my nerves would be tested, Barnes said. I wouldnt have liked to bogey the last hole and end it that way. But Ive got to go back, take my shoes off and think, Hey, I shot even par on Saturday with the lead. If I go out and do the same thing, someone is going to have to really come back low to catch me.
While it was another four shots to find the next group of challengers, they were optimistic ' particularly Phil Mickelson.
Mickelson, determined to finally bring home a U.S. Open trophy to a wife battling breast cancer, knocked in a 30-foot birdie on the 16th hole and finished with a 35-foot birdie on the final hole to shoot 69, leaving him six shots behind.
He made his share of mistakes, as always. But he also made seven birdies.
Im one good round away, Mickelson said. I feel like if I can get a hot round going, I can make up the difference.
David Duval, winless in eight years and now No. 882 in the world ranking, continued to stay in the picture. Right when he looked to be fading, he carved a shot out of the trampled rough and around the trees to 10 feet for birdie on the 16th, then stuffed a 7-iron into seven feet on the final hole for another birdie and a 70. He was at 3-under 207 with rising star Ross Fisher of England, who had a 69.
The fourth round started at 5:45 p.m., with the leaders likely to get in only a couple of holes before darkness forced them to return for a Monday finish.
Eleven players remained under par, a group that did not include defending champion Tiger Woods.
Woods made only one mistake ' taking two hacks with the wedge to escape knee-high grass around the 14th green ' but more troubling was that he made only three birdies after giving himself so many chances inside 15 feet. He had to settle for a 68 and was nine shots behind. He has never won a tournament trailing by more than eight going into the final round.
Obviously, its not totally in my control, said Woods, at 1-over 211. Only thing I can control is whether I can play a good one or not.
Control belongs to Barnes, although not as much as he would have liked.
He set the 36-hole U.S. Open scoring record, then looked as though he might shatter several more when he rolled in a 25-foot eagle putt at No. 4 to reach 11 under. The only other players to be double digits under par at a U.S. Open were Gil Morgan (1992), Tiger Woods (2000) and Jim Furyk (2003). Woods is the only player to finish there.
But with a six-shot lead at the turn, Barnes suddenly looked shaky.
He hit only three fairways on the back nine, and birdie chances were limited. He steadied himself with a good chip to 4 feet for birdie on the par-5 13th, and rolled in a 35-foot birdie from behind the hole at the par-3 17th.
But from the 18th fairway, his approach buried in deep grass and he missed the par save.
Glover closed on him quickly, shooting a 32 on the back nine to get back in the game. He went into the final round feeling as though no one was giving him a chance to win ' not with such an unlikely leader in Barnes, and so many other All-Stars behind him like former Masters champion Mike Weir in the group at 208, two-time U.S. Open champion Retief Goosen at 209, even Woods.
First time I made the cut at an Open. Won one tournament, Glover said, listing a few reasons to have so little hope. But Ricky and I, we are playing better than everybody right now. Again, weve got the fourth round together.
And it will be a fourth round over two days, the first time that has happened since Larry Nelson won at Oakmont in 1983.
Most players had a hard time remembering what day it was in this on-again, off-again Open in which no round has been completed on the day it started. There was another 4 1/2 -hour delay Sunday morning because of nearly an inch of rain overnight.
Mickelson has a tropical vacation planned with wife Amy and their three children before her July 1 surgery for breast cancer, although he was in no hurry to get home now. He has been runner-up four times in this major ' already tied for the record ' and talked earlier this week about his wife leaving him messages to bring home the silver trophy.
Even six shots behind ' the largest final-round U.S. Open comeback is seven shots in 1960 ' Mickelson could practically taste it.
Anything can happen in a U.S. Open, Mickelson said.