Harman might be the surprise leader after three rounds at the U.S. Open, but there was nothing ordinary about his game.
Day has not missed a first round major cut since 2012 and Johnson won the U.S. Open in 2016.
Thomas, 24, who shot 59 earlier this year in Hawaii, was 9-under on the par-72 course, eclipsing the U.S. Open record for lowest round in relation to par, set by Johnny Miller at Oakmont (par-71) in 1973.
This was Reed's day before Thomas raised the bar, Fleetwood refused to be intimidated - aside from one aberration on his final hole - and Harman flew under the radar.
WEDDING BELLS: Nick Rogness had one of the biggest plays of the day.
On Friday, the 39-year-old responded to a similar situation with a run of five successive birdies but he was unable to replicate that on Saturday, as he ended the round on four under par.
Thomas poured that in to become the 29th player with a 63 in a major championship.
On that occasion Arnold Palmer, Gary Player, Hale Irwin and Ray Floyd shared the halfway lead, with Irwin going on to win the "Massacre at Winged Foot" on seven over par. Felt like I had a good feel for the speed of the greens today, hit a lot of good lag putts. -Thomas on the meaning of his record-setting 63. Every time I've been in majors so far I've put so much emphasis on them and tried so hard at them that I kind of got in my way.
Only eight shots separate the leaders from the players who made the cut on the number. "It sets up really well for me, especially if I'm driving it like I did today". I'd love to have another one of those. The final round on Sunday looks to be another mostly dry day.
None of the dozen have won a major, and neither have the four non-Americans (Fleetwood, Kim Si-woo, Bernd Wiesberger and Hideki Matsuyama).
"It's been an off-putting week for me", Spieth said. "But I'm looking forward to getting the job done".
The highlight of a round which included nine birdies and two bogeys was a magnificent eagle-three on the par-five 18th.
But Oostihuizen knows how quickly momentum can swing at a U.S. Open.
Furyk reached 10-under 200 with a 67 in the third round at Olympia Fields, giving him a three-shot lead over Stephen Leaney of Australia.
Li found the rough with his tee shot on 18 and hacked it out with an 8-iron, but his ball settled into a deep divot on the fairway, before his third shot bounded through the green into more nasty grass, from where he took six more shots to hole out for a 10-over 82 at Erin Hills. On the day, No. 5 yielded 25 birdies, 111 pars and 20 bogeys.
He says he feels comfortable on the course, and now that he spent Saturday booking his place in history, he wants to follow a similar fate on Sunday.