One of 11 players who navigated the TPC at Summerlin without a bogey Saturday, McCarron established a 72-hole tournament record at 26-under 261. He has gone 58 holes without a bogey after compiling a 74-hole streak earlier this season.
"I enjoy playing the (TPCs)," McCarron said. "I can reach most of the par-5s."
The top 30 players on the PGA Tour money list earn spots in the lucrative Tour Championship. McCarron arrived here in 34th place with $1,396,178. First prize is $810,000.
"(This tournament) gave me an exemption my first year on tour. I finished third to keep my card. It's been big for my golfing career," he said. "I will be here every year."
Former PGA Player of the Year Tom Lehman was second at 23-under 264, following a 72 with a 67 to finish the day where he started it.
"I thought I played well. Three bogeys hurt, but eight birdies made up for it," Lehman said. "I'm disappointed with the bogeys I made. But I'm in a good position, three back. You can go low here."
Bob Estes shot a 68 for his 16th consecutive round in the 60s and was tied for third at 21-under with South Africa's Rory Sabbatini and third-round leader Craig Parry of Australia.
Sabatini overcame Achilles tendinitis with a career-best 63, but Parry managed just a 70.
"I have a little inflammation and tendinitis in my (right) Achilles tendon," Sabbatini said. "It's not affecting my golf swing, but it really affects me when I walk. It's actually been an advantage because it takes my mind off my shots. It makes me take it one shot at a time."