Matthew Wolff equalled a U.S. Open record and is on track to make further history after taking a two-stroke lead in the third round.
Wolff carded a five-under 65 on Saturday, equalling the lowest round produced at Winged Foot at a U.S. Open.
The 21-year-old American blitzed the front nine in New York, making five birdies before a consistent back nine included a bogey and birdie.
Wolff's round came after hitting just two of 14 fairways, but he reached five under and a two-shot lead.
His 65 matched the round Justin Thomas managed on Thursday to set the record at Winged Foot.
If he wins, Wolff would become the first player to claim the U.S. Open on tournament debut since Francis Ouimet in 1913.
Bryson DeChambeau (70) sits second at three under and Louis Oosthuizen (68) is the only other player under par at one under.
DeChambeau opened his round with back-to-back bogeys before picking up a shot at the seventh.
The American then made birdies at 16 and 17, but could only manage a bogey at the par-four 18th.
Oosthuizen, the 2010 Open Championship winner, is also in contention after mixing four birdies with two bogeys.
Hideki Matsuyama (70), Xander Schauffele (70) and Harris English (72) are at even par, a shot ahead of Rory McIlroy (68).
But it was a forgettable third round, and in particular back nine, for overnight leader Patrick Reed.
The 2018 Masters champion was one under through nine holes before falling apart to shoot a 77 and sit at three over, tied for 11th.
Reed bogeyed six of his final nine holes and had a double bogey at the 11th, where he struggled to recover from the rough.
Thomas is at four over, while world number one Dustin Johnson was again unable to get much going, shooting a 72 to be at five over.