Kelly Kraft missed the chance to take the sole lead into the final round of the Greenbrier as he bogeyed the 18th hole in West Virginia.
The American dropped his only two shots of the third round on the 16th and 18th, which left him 14 under par alongside compatriot Harold Varner.
Varner parred his first 10 holes of the day before picking up shots on the 11th, 12th, 14th and 17th.
Kraft, who like Varner is chasing a first PGA Tour title, had led by a shot going into the round, with American Webb Simpson and India's Anirban Lahiri his closest challengers.
Lahiri is now three shots off the pace after posting a one-over 71, but Simpson's challenge appears to be over after he dropped six shots in his 76, including a double-bogey on the 17th.
Xander Schauffele and Kevin Na are both a shot off the leading duo, while two-time major winner Bubba Watson is three shots back after posting a five-under 65 on Saturday.