Justin Leonard shot a six-under-par 66 to move to 23-under and build a four-stroke lead going into the final round of the Bob Hope Chrysler Classic.
Robert Gamez, DJ Trahan, Anthony Kim and Kenny Perry are tied for second on 19 under par as the quartet failed to capitalise on a number of opportunities.
Gamez was the third-round leader in the five-day pro-am event but shot a three-over-par 39 on the front nine and had to scramble to finish with a one-under 71.
Trahan was two strokes behind Leonard but bogeyed his final hole while Leonard birdied his for a two-shot swing.
Kim struggled from inside 10 feet with his putter for the second consecutive day but nevertheless matched Leonard's 66 to move from a tie for fifth to a share of second going into the final round.
Leonard, an 11-time PGA Tour winner, is now 18 holes away from not only winning this event for the second time in four years, but capturing a tour event for the second consecutive year.
"I'd like to think I am heading down that path," said Leonard, who is looking for his first victory since the Valero Texas Open last October.
"I don't want to think too much about it but I feel I am on the verge.
"You can make a lot of birdies here.
"Whether the lead was one shot, two shots, 10 shots, I've got to go out there with the same attitude that I've had.
"Just go play and try and play well and see if it's enough."
Gamez, who carded his worst round of the tournament, said: "I struggled a little bit early on. I just never really did anything until the back nine."
Kim revealed he had adopted a safety-first approach to his putting.
"I just wanted to make sure that I gave every putt a chance to go in," he said.
"I felt like last year, I left too many putts on the lip.
"Four shots is a lot of shots. You never know what can happen, though.
"Hopefully, my game will be sharp and the birdies will come. I need to play well on the front nine and make some birdies on those holes."
Trahan was the most disappointed of all after a poor end to his round.
"Now I've got a lot more work to do," he said.
"Hopefully, I can go out and hit some quality shots and make some putts and give myself a chance."
Those who failed to make the cut at seven under par included Chris DiMarco, Mark Calcavecchia and Fred Couples, while John Daly withdrew before the start of the fourth round with a rib injury.