American trio Ben Crane, David Toms and Mark Wilson are tied for the lead at the half-way point of the Humana Challenge in California.
The group of three sit on 16-under after Friday's play, and have a handy three-shot advantage on the chasing pack as they head into the final two days.
Colombian Camilo Villegas is in a tie for fourth with another three players from the United States - in Harris English, Chris Kirk and Bobby Gates - though he did drop back slightly on the second day of the tournament.
Wilson was the best of the leaders, shooting a blemish-free 62 that included eight birdies and one eagle.
A hat-trick of birdies started his day in superb fashion, and he made up more strokes on holes six, eight and 10 before he followed with an eagle.
He then was able to keep his composure late in the round to capitalise on his good work while Crane - who shot a magnificent 63 - made two late bogeys to rob him of a chance of holding the outright lead.
Toms enjoyed an outstanding run from holes seven to 10, where he went birdie, eagle, birdie, birdie en route to his seven-under 65.
For the second day running, Villegas did not drop a shot as he fired a 68. In the in the group of players tied for fourth, Gates and Kirk each shot 63.
English went one better in his 10-under 62, with his round including a run of five birdies in succession.
Americans Cameron Tringale, Chris DiMarco, Ken Duke, Tommy Biershenk, Brandt Snedeker and John Mallinger are all at 12-under and in a tie for eighth, while Zach Johnson and Australian John Senden are a shot further back among a nine-way tie for 14th.
Ryan Moore of the United States is also in that group and he hit the best round of the day, recovering from two early bogeys to post an 11-under 61.
His round included a run of 11 birdies in 12 holes.
Defending champion Jhonattan Vegas of Venezuela is in a tie for 114th at two-under, while world number eight Dustin Johnson - the highest-ranked player in the field - withdrew after his first-round 72.