15 and 16 to finish five shots off leader Bud Cauley heading into Friday.
Dufner, who is seeking his fifth PGA Tour victory, overcame three front-nine bogeys with two eagles, one of them by holing a 99-foot pitch at the fifth hole.
Donald, a five-time victor on the USA tour, has six top-three finishes at Harbour Town Golf Links, most recently claiming a share of second a year ago.
DeLaet was second after a 69, the Canadian's third straight sub-70 round after having just five in five previous appearances here.
Donald also shot 67 to reach 10-under 132, two in front of Ian Poulter and Webb Simpson.
Matt Kuchar, fresh off a tie for fourth at the US Masters where his final-round 67 matched the day's lowest score, shot a three-under-par 68 and was tied in 19th place along with South Africa's Branden Grace, twice victor Jim Furyk and twice major victor Martin Kaymer of Germany.
Poulter, playing on a medical extension, needs to earn $145,000 or 117 FedEx Cup points over the next two weeks to keep his playing privileges intact. On the 15th, the course's final long hole, Dufner settled for birdie, one of three in a row on the back nine that took him into the lead.
Graham DeLaet of Weyburn, Sask., started the day one shot off the lead but a final round 73 dropped him into a tie for sixth.
CHAMPIONS TOUR: Bob Tway bogeyed two of the last three holes and settled for a 7-under 65 in the Mitsubishi Electric Classic in Duluth, Georgia.
"This place has been kind to me". Jimenez won in 2014 at TPC Sugarloaf and is coming off a victory in the Mississippi Golf Resort Classic.
Defending champion Woody Austin opened with a 69. He also had to make birdie on the last hole of his final round to force the playoff with Molinari.
The Frenchman made four birdies and an eagle and was one stroke ahead of Denmark's Lucas Bjerregaard (71) and South Africa's Trevor Fisher Jr.
Oahu, United States: South Korea's Kim In-Kyung vaulted into a share of the lead with a sizzling eight-under 64 in Thursday's second round of the LPGA Tour's Lotte Championship. Simpson, who is a North Carolina native, was a runner-up at this tournament in 2013 after falling in a playoff to Graeme McDowell. "I don't know when the last time we had two winners on tour the same year, maybe back with [Stephen] Ames and [Mike] Weir".
Dufner began Saturday three shots off the pace set by DeLaet and Donald, but moved to the top of the leaderboard at 13 under courtesy of the low round of the day, a six-under 65.