Brian Harman opened up a one-shot lead at the 117th US Open on Saturday in a dramatic third round lit up by a record-equalling 63 from Justin Thomas.
Torrential rain that doused the 7,818-yard layout at Erin Hills overnight presented the field with a feast of birdie chances, transforming the leaderboard into a sea of red as dusk fell.
Harman, who had begun the day in a four-way tie for the lead, carded a five-under-par 67 which included six birdies and one bogey.
The 30-year-old from Georgia had never gone past the second round in a US Open before this year, missing the cut on his two previous visits in 2012 and 2015.
"We're breaking down all kinds of barriers," Harman quipped.
"I'm proud of the way I hung in there today. I got off to a pretty good start, which I really haven't done yet, so that was nice.
"Struck it well, hit a bunch of greens, and that's what you've got to do to play well around here."
The world number 50 headed to the clubhouse on 12 under, one ahead of Thomas, Brooks Koepka and England's Tommy Fleetwood.
The soft, forgiving conditions created opportunity for major movement up the leaderboard for those players willing to take it.
And the prime beneficiary was Thomas, who catapulted up the leaderboard with his record-breaking nine-under-par 63.
The 24-year-old world number 13 produced a magnificent eagle three on the 600-yard 18th hole to crown a spellbinding display that was the lowest to par score in US Open history.
The previous lowest score in relation to par was the eight-under 63 shot by Johnny Miller in the final round of the 1973 Open.
Thomas was already on course for a share of the lead as he stepped up to the 18th having carded nine birdies against two bogeys in a spectacular round.
He then drilled a 300-yard second shot to around eight feet before rolling in his eagle putt to roars from the galleries.
"I feel comfortable. Being in contention in a major is new and I'm excited," said Thomas.
"I hope the moment will come as soon as possible. I know I'm going to be nervous, I just need to harness that as best I can."
Rickie Fowler was two behind Harman on 10 under after a four-under-par 68 which kept him firmly in contention.
Fowler likes his chances of breaking his major duck on Sunday.
"It's going to be a really cool day for someone tomorrow," the world number nine said.
"I'm looking forward to my shot at it. It's not going to be an easy day, for sure. I've been there a handful of times and had some good finishes. But I'm looking forward to getting the job done."
South Korea's Kim Si-Woo was one behind Fowler on nine under after also shooting 68, while three players — Patrick Reed, Russell Henley and Charley Hoffman were on eight under.
Reed was one of the biggest movers, powering up the board with a dazzling seven-under-par 65 that included four birdies on the front nine against one bogey.
The American Ryder Cup star then bagged a trio of birdies on the 14th, 15th and 16th holes to finish at eight under.
The low-scoring sets up a wide open final Sunday, with the world's top three ranked players — No.1 Dustin Johnson, No.2 Rory McIlroy and No.3 Jason Day — all missing the cut on Friday.
None of the leading 16 players have won a major before, making it likely that a run of six consecutive victories by first-timers will extend to seven this weekend.
South Korea's Kim will lead the Asian quest for a major on Sunday after Hideki Matsuyama was unable to build on his second round 65.
Matsuyama, the world number four, had to settle for a one-under-par 71 which left him on six under, six off the pace.
Elsewhere, Masters champion Sergio Garcia finished with a 71 to stay on six under, six behind Harman.
China's Li Haotong, who on Friday became the first player from mainland China to make the cut at a major, bombed out of contention with a 10-over-par 82.