FORT WORTH, Texas, May 25, 2012 (AFP) - Dufner, who led by two strokes when the day began, stood on 15-under 195 after 54 holes at Colonial with 2007 Masters champion Zach Johnson, seeking his second Colonial title in three years, one stroke adrift after a third-round 65.
"There has been a lot of good golf and I have a lot of confidence going to the first tee on Sunday," Dufner said.
American Tom Gillis was a distant third on 203, one stroke ahead of Bo Van Pelt, with Ryan Palmer and John Huh on 205 on the all-American leaderboard.
Dufner won his first US tour title in his 163rd try on April 29 with a playoff victory at the Zurich Classic in New Orleans.
Last weekend he joined compatriot Hunter Mahan as this year's only repeat US PGA winners by taking the Byron Nelson crown. A victory on Sunday would make him the first triple-winner in a US PGA season since Jim Furyk in 2010.
"I've just been working really hard on my game," Dufner said. "Breaking through at Zurich a few weeks ago really gave me some confidence and I'm just trying to run with it."
Dufner, who has led or shared the lead after 12 of his past 35 rounds, squandered a late lead in last year's PGA Championship and shared 24th at the Masters after being a 36-hole co-leader at Augusta National.
Dufner, who was married a week after his victory in New Orleans, is trying to join legendary Ben Hogan as the only players to win both US PGA events in the Dallas-Fort Worth area in the same year.
Hogan won the Colonial and the Dallas Invitational, which later became the Byron Nelson Classic, in 1946. Dufner would be the first player to win the North Texas events in consecutive weeks.
Dufner opened with a birdie at the par-5 first and added another at the seventh while Johnson opened with back-to-back birdies and added another at the fifth to match playing partner Dufner for the lead at 12-under.
Dufner birdied the seventh but Johnson again matched him for the lead by sinking a 26-foot birdie putt at the ninth, leaving them deadlocked at 13-under and five strokes clear of the field as they began the back nine.
"The front nine I hit the ball pretty good, gave myself some opportunities," Johnson said. "The back nine was certainly a battle."
At the 10th, Dufner curled in a 20-foot birdie putt to grab the lead. Dufner sank a four-foot birdie putt at the par-5 11th after Johnson missed a seven-foot birdie putt, boosting Dufner's advantage to two strokes.
Dufner dropped his approach four feet from the cup at the 12th and sank the birdie putt for a three-stroke edge.
"It helps to be here this week and have good control of my golf ball," Dufner said. "You have to have good control of your swing and I have that right now."
Dufner missed a six-foot par putt at 14 but Johnson also took a bogey.
Johnson bounced back by sinking a 17-foot birdie putt at the par-3 16th while Dufner made a bogey, missing from seven feet for par, and suddenly Dufner was at 14-under and only one stroke ahead of Johnson.
On the 17th green, Johnson's approach nudged Dufner's ball with both about eight feet from the cup. After resetting Dufner's ball, Johnson sank the birdie putt and moments later Dufner nabbed his own birdie to preserve his lead.
Leading scores after Saturday's third round of the $6.4 million US PGA Crowne Plaza Invitational at Colonial (USA unless noted, par-70):
195 - Jason Dufner 65-64-66
196 - Zach Johnson 64-67-65
203 - Tom Gillis 65-69-69
204 - Bo Van Pelt 69-64-71
205 - John Huh 70-66-69, Ryan Palmer 68-67-70
206 - Kelly Kraft 71-71-64, Jonas Blixt (SWE) 73-67-66, Jim Furyk 69-69-68, Louis Oosthuizen (RSA) 71-67-68, Ryan Moore 67-69-70, Rickie Fowler 68-68-70, Tommy Gainey 66-67-73
207 - Jonathan Byrd 72-68-67, Kevin Chappell 70-67-70
208 - David Hearn (CAN) 71-72-65, Yong-Eun Yang (KOR) 73-69-66, Corey Pavin 71-70-67, Matt Kuchar 72-69-67, Hunter Mahan 69-71-68, Sunghoon Kang (KOR) 70-69-69, Charley Hoffman 69-70-69, Greg Owen (GBR) 69-68-71, Harris English 65-70-73
209 - Ken Duke 68-75-66, Chris Stroud 69-73-67, Roberto Castro 67-74-68, Ben Crane 70-71-68, Brendon de Jonge (ZIM) 67-74-68, John Daly 70-69-70, Vijay Singh (FIJ) 70-69-70, David Mathis 71-67-71, Kyle Reifers 65-72-72