PGA Tour rookie Michael Thompson moved one shot clear after Saturday's third round of the McGladrey Classic at St Simons Island in Georgia while fellow American Webb Simpson stayed in the hunt for his third victory of the year.
Thompson fired a three-under-par 67 on another breezy day at the Sea Island Resort to overhaul second-round pacesetter Billy Horschel and post a 13-under total of 197.
American Horschel, a stroke in front of Thompson with three holes to play, doubled-bogeyed the 16th after dumping his tee shot into water on the way to a 70 as he ended the day in second place at 12 under.
Simpson, who has won twice in his last five starts and has a chance to beat world number one Luke Donald of Britain to the PGA Tour money-list title, was a further stroke back after carding a 69.
"My caddie and I had a tough time reading the greens," Simpson told reporters after mixing three birdies with two bogeys. "I gave myself plenty of opportunities but the greens, as we get late into the week, are getting tough to putt.
"The goal for today was just to give ourselves a chance to win tomorrow. We hung in there and stayed in the golf tournament. That's all you can ask."
Simpson trails money-list leader Donald by $68,971 and both are scheduled to compete in next week's season-ending Disney Classic at Lake Buena Vista, Florida.
Thompson, who has recorded just one top-10 finish on the PGA Tour after 23 starts this season, was delighted to be in position to claim a breakthrough victory.
"I've just got to try to hit solid golf shots tomorrow," said the 26-year-old who lipped out with a nine-foot birdie putt at the last that would have given him a two-stroke lead.
"I was kind of struggling coming down the stretch there but tomorrow is a new day and I'm going to enjoy it."
Former U.S. Masters champion Trevor Immelman equalled the course record with a sizzling 62 to finish level with Simpson at 11 under.
"That's always going to help your round," South African Immelman said after covering his last five holes in six under.
"I played real well today, drove the ball well, hit some nice iron shots and made some putts. It really was a fun day."
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