Troy Matteson shot a 3-under-par 68 for a one-stroke lead over Jeff Maggert and Brian Harman after two rounds of the John Deere Classic on Friday.
Matteson was at 13-under 129.
Maggert's bogey-free round of 9-under 62 moved him from 39th place after the first round to a tie for second. He birdied half the holes at TPC Deere Run, including five of his last nine.
Harman had a second straight 65, the last two of his seven birdies coming after a 48-minute thunderstorm delay.
Matteson bogeyed the par-4 18th after getting four birdies in the first 17 holes.
J.J. Henry, Gary Christian, Robert Garrigus and Ricky Barnes are tied for fourth at 11-under 131.
A trio of players are at 10-under 132, including three-time defending champion Steve Stricker, whose 4-under 67 placed him within striking distance with 36 holes to play. Tommy Biershenk and two-time U.S. Open champion Lee Janzen are also at 132.
Zach Johnson shot 6-under 65 and was at 9-under 133.