Jason Dufner shot a 7-under par 65 at the Stadium Course at PGA West, the most difficult of the three courses, to take the lead at the halfway point of the CareerBuilder Challenge in La Quinta, Calif.
Dufner, seeking his first victory since he won the PGA Championship in 2013, got off to a hot start with five birdies on the front nine, and through 36 holes sits at 15-under par, one stroke ahead of Jamie Lovemark.
Phil Mickelson, meanwhile, shot a 7-under-par at the Nicklaus Tournament Course, and is at 11-under in his first start of 2016. He climbed to a tie for eighth place, four strokes behind Dufner.
"So, now the swing is back on plane and I'm just working on touch," Mickelson said. "I'm just trying to get the front nine tuning of feeling the subtleties and nuances of hitting those little shots, which I have been struggling with these last couple years because, again, I've been a little bit off plane."
The best round of the day belonged to Jason Gore who shot an 8-under 64, bringing his score to 12-under. He is tied for third with Adam Hadwin, Bill Haas, Adam Loupe and Anirban Lahiri.
Patrick Reed, who won this event in 2014, shot a 69 on the Nicklaus Tournament Course and is 10 strokes off the lead.