Robert Garrigus fired a 6-under 64 on Saturday to take a 1-stroke lead after three rounds of the Canadian Open.
Garrigus, who will go for his second PGA Tour win on Sunday, finished 54 holes at 16-under-par 194.
His total of 194 broke the tournament's 54-hole scoring record. Arnold Palmer first set the mark of 195 in 1955 and Dean Wilson matched that total in 2010.
Second-round co-leader William McGirt posted his second straight 66 to end three rounds at minus-15. Scott Piercy, who led after round one and shared the second-round lead, shot 67 for the second day in a row and is alone in third at 14-under-par 196.
Scott Stallings and Chris Kirk both fired 7-under 63s Saturday. They share fourth place at minus-12 with Bo Van Pelt, who posted a 67 at Hamilton Golf & Country Club.
Piercy, who played in the final group with Garrigus and McGirt, grabbed the early lead with a birdie at the first, but he stumbled to a bogey on No. 3.
The trio all took advantage of the par-5 fourth. Piercy and McGirt made birdie to move to 12-under, while Garrigus kicked in a short eagle putt to join them there.
All three birdied the short par-4 fifth. McGirt made it three in a row with an 18-foot birdie putt at the sixth that gave him a 1-shot lead.
Piercy joined him atop the leaderboard with a birdie at the eighth, but two bogeys in his next five holes dropped Piercy three back.
Garrigus and McGirt traded birdies at nine and 10, but only Garrigus could keep the hot play going. He rolled in a birdie putt from just off the green at No. 11. Garrigus came right back with a birdie on 12 to grab a 1-shot lead.
McGirt fell two back as he failed to get up and down for par from a greenside bunker on the par-3 13th. He inched back within one with a 14-foot birdie putt on the par-3 16th.
Garrigus two-putted for par on his final six holes to end at 16-under.
"It was good to great," Garrigus said of his putting in a television interview. "I made a couple of long ones, which you need to make. When you make long putts and you're in contention, it puts you up there. I felt like I putted well today. I didn't have a three-putt and didn't have a bogey."
McGirt, who is playing his 23rd event of the year, parred his last two to finish one back.
"My legs are a little bit tired right now, and mentally I'm a little tired because of being in the mix last week and all week being right there, here," McGirt said in a TV interview. "I just have to keep playing my game and take advantage of the opportunities that I get."
Piercy rallied with birdies at 15 and 17 to post 14-under through three rounds.
Ryan Palmer (64), J.B. Holmes (64), Josh Teater (68) and Bud Cauley (67) share seventh place at 10-under-par 200.
NOTES: Garrigus' lone PGA Tour title came at the 2010 Children's Miracle Network Classic...McGirt played in the final group on the weekend for the first time in his PGA Tour career.