American Kelly Kraft will take a one-shot lead into the weekend at the Greenbrier.
The former US Amateur champion carded a second-round 63 in West Virginia to advance to 13 under par for the week.
The 29-year-old, chasing a first PGA Tour title, lies a stroke clear of compatriot Webb Simpson and India's Anirban Lahiri.
Kraft carded four birdies in a front-nine 30 and holed a five footer at the 11th, before dropping his only shot of the day on the 12th after a wild tee shot was followed by finding a bunker with his third.
He responded with three birdies in his next four holes, the highlight an approach to six feet at the 16th.
Lahiri had nine birdies in a flawless 61, while former US Open champion Simpson mixed six birdies with a bogey on the 13th and a double bogey seven on the 12th after taking four shots to find the green and three-putting in an eventful 67.
American Jason Kokrak lies fourth on 11 under following a 64, one ahead of compatriot Harold Varner III and Korean Whee Kim