Erik Compton is in the hunt to win his maiden PGA Tour title, but he shares the Humana Challenge lead with three others after the third round.
Compton carded a five-under 67 on the PGA West Nicklaus Course in California on Saturday.
But three of his American countrymen join him atop the leaderboard at 17 under.
Bill Haas (69) also played the Nicklaus course in his third round, while Justin Thomas (68) and Michael Putnam (69) had solid outings.
Compton went through bogey-free, with birdies on the third, 10th, 14th, 16th and 17th holes the highlights of his round.
He was a runner-up at the US Open last year and has previously undergone two heart transplants.
Haas, the 2010 champion, bogeyed the 11th but was otherwise similarly impressive.
On the PGA West Palmer Course, Thomas produced six birdies and two bogeys.
Putnam, whose nine-under 63 in the opening round set up his tournament, managed a 69 at the La Quinta Country Club.
Americans dominate the leaderboard and four more are tied for fifth.
Matt Kuchar (71) is alongside Ryan Palmer (68), Scott Pinckney (69) and Steve Wheatcroft (68) at 16 under.
Kuchar bogeyed three of his final four holes on the Palmer course.
The packed leaderboard also has a group of seven players at 14 under.
Among that group is defending champion Patrick Reed, who carded a five-under 67.
South African Rory Sabbatini surged into that group with a nine-under 63 that included six birdies on the back nine of the Nicklaus course.
German Alex Cejka (70), Italian Francesco Molinari (67), Nick Watney (71), Martin Laird (68) and Park Sung-joon (67) are also at 14 under.