Jay Haas fired a six-under 65 Saturday to grab a three-stroke lead with one round to go at the Principal Charity Classic.
Haas finished two rounds at 11-under 131 and will go for his 16th Champions Tour win on Sunday.
Larry Mize posted a three-under 68 to remain in second place at minus-eight. He is one stroke clear of Tom Lehman, who carded a four-under 67.
Andrew Magee, who is making his second Champions Tour start, shot his second straight three-under 68 to move into fourth place at six-under 136.
First-round leader Mike Goodes stumbled to a three-over 74 that dropped him into a share of ninth at minus-four at Glen Oaks Country Club.
Haas, the 2007 and 2008 winner, started the round two strokes behind Goodes, but grabbed the lead by the fourth hole. Haas poured in a 40-footer for birdie on No. 3 to move to minus-six.
After he parred the fourth, Haas was alone in the lead thanks to bogeys at two and three by Goodes.
Haas pulled away from the field quickly. He ran home another long birdie effort on the fifth before dropping a wedge shot to eight feet at the seventh.
He converted that putt, then sank a five-footer for eagle on No. 9 to head to the back nine at 10-under.
Haas missed four birdie chances inside 10 feet on the back nine, but sank a five-foot birdie try on the 16th to move to minus-11.
"I played very well today. I made some nice long putts on three and five," Haas said. "The wind made it difficult today. Things go your way when you shoot a low score like today."
Mize birdied the fourth, but gave that stroke back with a bogey on the par- four sixth. He birdied the par-five ninth to make the turn at seven-under.
The former Masters champion converted another birdie on a par-five at 15. After tripping to a bogey on 17, Mize holed his five-iron approach shot for eagle on the par-four 18th.
"I had a good distance (177 yards) for a five-iron into the last hole. I was just trying to hit a good shot in there, trying to make birdie and sure enough the hole got in the way and it went in for two," Mize said of his shot on the 18th. "There were still a few loose shots that I would like to hit a little better."
NOTES: Haas has held the lead by himself going into the final round eight times on the Champions Tour and has won five of them. He has gone 174 holes without a three-putt...The winner has come from the final group in 19 consecutive Champions Tour events.