John Mallinger matched the course record on Friday as he fired a 9-under 62 to move four strokes clear of the field after two rounds of the Frys.com Open.
Mallinger finished 36 holes at 14-under-par 128, and set a new scoring record along the way.
His 62 tied the course record at CordeValle Golf Club. Will MacKenzie and Jim Renner set the mark last year, and Nick O'Hern matched in the first round on Thursday. Mallinger's 36-hole total of 128 set new tournament record by one shot. Five players had posted 129 for the old record.
"Well, it's only the second time I've shot 62 in seven years out here, so not very often. Any time you get it that low, everything was kind of clicking," said Mallinger. "Drove it great, irons were great, and made putts."
Billy Horschel (65) and Jhonattan Vegas (67) share second place at minus-10.
O'Hern, who led by three after the opening round, managed an even-par 71. He slid into a share of third at 9-under-par 133. He was joined there by Scott Dunlap (63) and Nicolas Colsaerts (68).
Mallinger got on the board with a 16-foot birdie putt at the second. After four pars in a row, he kicked in a short birdie effort at seven and followed with a 12-footer at the eighth to move to 8-under.
After pars at nine and 10, Mallinger grabbed a share of the lead thanks birdies at 11 and 12.
Mallinger, who shared second at the Humana Challenge earlier this year, jumped into the lead at the par-5 15th, when his 11-foot eagle putt found the bottom of the cup.
He pushed his lead to four with birdies on the last two holes.
"I think was the eagle probably on 15. I hit a great 5-wood in there about 10 feet above the hole and made a great putt," said Mallinger of the key shot down the stretch. "Then I hit it close on 17, tap-in on 18."
Horschel, who stands 147th on the money list and needs a good finish to keep his tour card for next year, bogeyed the first before he parred the next six holes.
From there, Horschel flew up the leaderboard. He birdied the eighth and ninth to make the turn at 5-under. He birdied the 12th, then drained four birdies in the last six holes to soar in to a share of second place.
His birdie on 17 was an adventurous one as his drive went well left, but he got a drop from an animal hole.
"I was into the left side of the green, had the face open, and was just trying to swing as hard as I could and get it somewhere near the green and not have it go in the water," Horschel said of his second to the 17th. "It came out perfect and obviously caught the backslope and rolled down to a couple feet. It was more luck than skill."
Vegas had three birdies in a 4-hole stretch from the 12th. That run ended with a bogey on the 16th, but he erased that mistake with a bogey on No. 18.
On the front side, he had two birdies and two bogeys through eight holes. Vegas stuffed his third shot at the par-5 ninth within a foot and kicked that in for a closing birdie.
NOTES: Mallinger, who is winless on the PGA Tour, has the 36-hole lead for the third time in his PGA Tour career...Ryan Moore first set the old 36-hole scoring record of 129 in 2007 and he was later matched by Arron Oberholser, Rickie Fowler, Greg Owen and Rocco Mediate...The cut line fell at 1-under-par 141 with 72 players moving on to the weekend...Among those missing the cut were Mike Weir, Rory Sabbatini, Robert Allenby, Ricky Barnes, Chad Campbell, John Daly and Trevor Immelman.