Phil Mickelson posted a 5-under 67 on Friday and moved two strokes clear of the field at the Wells Fargo Championship.
Mickelson completed 36 holes at 9-under-par 135.
Scott Gardiner matched Mickelson's 67 to move into second at minus-7. He was joined there by George McNeill (68) and Nick Watney (70).
Rory McIlroy, who was one of seven first-round co-leaders and the 2010 champ, managed a 1-under 71 and dipped into a share of fifth at 6-under-par 138. He stands alongside Rod Pampling (69), Lee Westwood (68), Jason Kokrak (70) and Derek Ernst (71).
Mickelson started his round with a 13-foot birdie putt at the first. He came right back with a birdie from 14 feet out on No. 2.
The 2010 runner-up ran off four pars in a row before converting a 9-footer for birdie at the seventh. At the ninth, Mickelson ran home a 39-foot birdie chance to make the turn at 8-under.
Mickelson found the left rough off the tee and dumped his second shot at the par-4 12th in a greenside bunker. He blasted to 11 feet, but 2-putted for bogey.
Two holes later, Mickelson drove into a greenside bunker on the short par-4 14th. He blasted to five feet and converted that birdie chance.
Mickelson made it two in a row as he got up and down for birdie on the par-5 15th from the right rough. He closed with three pars in a row.
"I have struggled off the tee for 27 holes. After the 10th tee shot, something kind of clicked in and I realized my alignment was a little off," Mickelson admitted. "I started hitting some good tee shots after that, and played the last eight holes better than I thought.
"I think this weekend, if I drive the ball the way I was driving it before I came here, and the way I started to the last eight holes, I think it's going to be a fun weekend."
Gardiner did all of his scoring on the front nine. He opened with a birdie on the first, then drained four consecutive birdie chances from the sixth to jump to 7-under. Gardiner closed his round with nine straight pars.
McNeill birdied the third, then wrapped birdies at the fifth and seventh around a bogey on No. 6. He birdied the ninth to head to the back nine at minus-6.
The two-time PGA Tour winner birdied the 10th, but stumbled to bogeys on the 11th and 12th to slip back to minus-5. McNeill rebounded with birdies on 15 and 17 to gain a share of second place.
Watney tripped to a bogey at the third, but bounced back with a birdie on the par-5 fifth. He stumbled to another bogey at the par-3 sixth.
Last year's 36-hole leader atoned for that mistake with birdies at seven and eight. Watney moved into a share of second at minus-7 with a birdie at the 12th. He parred the last six holes to end there.
"It wasn't quite as good as yesterday, but I guess that is to be expected after you play so well," Watney stated. "I'm happy with my position."
Defending champion Rickie Fowler carded his second straight even-par 72. He is tied for 47th at even-par 144.
NOTES: Mickelson has carded 31 rounds of par or better in his 38 competitive rounds at Quail Hollow ... He has converted 17 of his previous 29 36-hole leads into victories ... The cut fell at 2-over-par 146 with 83 players moving on to third round ... Among those that missed the cut were Rory Sabbatini, 2009 winner Sean O'Hair, Bubba Watson, Martin Kaymer and Chad Campbell ... With the large number of players making the cut, there will be a second cut after the third round, and that will reduce the field to the low-70 and ties.