Harold Varner jumped four spots on Saturday to be co-leader with Kelly Kraft after the third round of the PGA Tour event at The Greenbrier in West Virginia.
Varner had four back-nine birdies after 10 consecutive pars in his four-under 66.
Kraft led by as many as four strokes but bogeyed two of the final three holes to shoot a one-under 69.
Both were at 14-under, to lead by a shot.
Cameron Percy, Australia's only golfer to make the cut, struggled on the front nine but made two back nine birdies to sign for a one-over 71.
He is in a tie for 48th at four under.
Fifteen golfers were within five shots of the lead with defending champion Xander Schauffele and Kevin Na tied for third after they both shot 65.
Kraft and Varner are looking for their first PGA Tour wins in their 85th starts.
Since this tournament debuted in 2010, there have been four first-time champions but no third-round leader has won.
The tournament has been decided by two or fewer strokes every year and has gone to a playoff three times. The 2016 tournament was cancelled after floods.
The Old White TPC dried out on a sunny Saturday and scores weren't as low as the first two days when rains softened the course and yielded eight rounds of 63 or better.
Sam Saunders was alone in fifth place at 12 under after a 67.
Bubba Watson, a three-times winner this season, shot 65 and was among three players at 11 under.
The top four players not already exempt among the top 12 finishers will earn spots in the British Open at Carnoustie starting July 19.
