Daniel Summerhays shot a 9-under 62 on Saturday for a two-stroke lead following third-round play at the John Deere Classic.
Summerhays, whose previous best finish on the PGA Tour was a tie for fourth, enters Sunday's final round at 19-under 194 and in position for his first career win.
Summerhays notched 10 birdies while matching the lowest third-round score in tournament history.
Canadian David Hearn (64) is second at 17 under.
Defending champion Zach Johnson held a share of the lead after each of the first two rounds, but he's now alone in third after shooting a 67.
J.J. Henry and Jerry Kelly are tied for fourth at 15 under.