Matt Kuchar leapfrogged fellow American Michael Putnam into the lead at the Humana Challenge as the Nicklaus course provided a lot of joy on Friday.
Kuchar was one of six players to complete the Nicklaus course at PGA West in La Quinta, California, and be in the top 11 after the second round.
The 36-year-old American started on the back nine and notched birdies on the 10th, 12th, 13th, 15th and 16th holes.
Birdies followed on the first and eighth holes, plus an eagle on the par-five fourth thanks to a 237-yard approach shot, although a bogey on the sixth provided one blemish for Kuchar in his eight-under 64.
But the Florida-born golfer claimed he is feeling comfortable with his game after moving a shot clear of Putnam at the top of the leaderboard.
"I've been feeling good. The game feels solid," Kuchar told the PGA Tour's 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."
Overnight leader Putnam produced a five-under 67 on the Palmer course to drop to equal second at 14 under overall, one stroke behind Kuchar.
Bill Haas joined Putnam at 14 under with a nine-under 63 at La Quinta Country Club - the Humana Challenge's first three rounds sees the field rotate around three separate courses.
Nick Watney (64), Justin Thomas (63) and Scott Pinckney (67) enjoyed the Nicklaus course to rise to 13 under overall, while Alex Cejka and Ryan Palmer were similarly impressive to reach 12 under.
Palmer posted the round of the day - an 11-under 61 - and Cejka carded a 64 to join Eric Compton and Steve Wheatcroft in a share of seventh.