Then Dufner grabbed a share of the lead with a three-iron to eight feet and a birdie on the long par-three 11th and, two holes later, birdied again from 10 feet to move ahead of first-round co-leader Adam Scott, who had shot 68 in the morning to go in front.
Another close iron approach, to six feet that set up a birdie at 16, had Dufner at seven under for the day, needing just one more birdie to post a 62, the lowest round ever scored in any of the four majors.
A solid par on 17 brought Dufner to the 18th, where he found the fairway and zapped an approach to 10 feet. Perhaps feeling the nerves, Dufner left the putt short, and settled for par and his 63.
“I knew that nobody had shot 62 (in a major),” said Dufner of the putt at history. “I just didn’t quite hit it (the last putt) hard enough.”
Much earlier in the day, Scott fought through heavy rain early in his round and followed up his opening 65 with a 68 to post 133, seven under par.
Scott chipped in for birdie on his first hole, the 10th, and he added a delicate downhill birdie putt on the par-five 13th and a third birdie on 16 as the rain persisted throughout his opening nine holes.
A bogey on the tough par-four 17th slowed up Scott, but he still turned in 33 and was up by two going to the front nine, where the rain finally started to diminish - much to the delight of fans who grabbed all the ponchos in the merchandise shop, causing them to run out.
Scott birdied 2 and made bogey on 3, and had another birdie-bogey exchange on 6 and 7 to finish at 68, but by that point, he was only one shot clear of his playing partner, U.S. Open champion Justin Rose.