Matt Kuchar carded an eight-under-par 64 to lead the Humana Challenge at the halfway stage in California.
Kuchar bettered his first-round effort of 65 by a shot to take a one-stroke lead on 15 under going into the weekend.
The tournament features three courses: La Quinta Country Club, PGA West Palmer, and PGA West Nicklaus.
All competitors will have played a round on each by the time the cut comes after Saturday's third round, and the final 18 holes are played out exclusively on the Palmer course.
Starting at the 10th hole on the Nicklaus course, Kuchar got off to a great start when he birdied at the first attempt before picking up shots at four of the next six to reach the turn in 31.
Kuchar proceeded to birdie the hole one to move to six under for the day and it got even better for the world number 11 three holes later when he eagled the par-five fourth to take the lead.
A bogey at the sixth was a temporary blip as Kuchar overcame that setback by picking up a shot on the eighth hole and parred the ninth to complete his fine round.
Kuchar moved a single shot ahead of first-round leader Michael Putnam, who followed up Friday's nine-under 63 with a solid 67 on the Palmer course which included five birdies.
"I've been feeling good. The game feels solid," Kuchar said on the PGA website. "I feel like I know where it's going, feel like I'm hitting it in the centre of the club face. I'm really pleased.
"I think everybody is really enjoying their time here."
Putman was tied for second on 14 under with the tournament's 2010 winner Bill Haas, who made seven consecutive birdies from the second at La Quinta to remain firmly in the mix with two rounds to play.
Nick Watney, Justin Thomas and Scott Pinckney were snapping at their heels on 13 under, while Ryan Palmer, Erik Compton, Alex Cejka and Steve Wheatcroft stood a further shot back.
Palmer was in sizzling form as he required just 27 shots to complete his first nine holes on the Nicklaus course. Starting at the 10th, he made two eagles and five birdies in an astonishing seven-hole sequence from the 12th.
And he birdied a further four holes but bogeyed a couple too on his way to a best-of-the-day 61.
Former world number one Luke Donald and five-time major winner Phil Mickelson remained off the pace.
Mickelson recovered from two early bogeys with five successive birdies on his way to shooting a six-under par 66 on the Nicklaus course that positioned him eight shots off the lead, in a tie for 36th place.
Seven shots further back in a tie for 127th stood Donald, who will do well to make Saturday's cut despite following up Friday's three-over 75 with a much more respectable 69 on the Palmer course.
