A three-under-par 67 kept Australia's Greg Chalmers on top of the leaderboard as the US Bank Championship in Milwaukee, Wisconsin, reached the halfway stage.
Chalmers had shared the first-round lead with American Jeff Klauk after both men shot six-under-par 64s at the 6,759-yard Brown Deer Park course on Thursday.
The Australian, playing the back nine first, overcame a bogey four at his fifth, the 14th, to card four birdies on the way to a second-round 67 to take the lead at nine under par for the tournament.
Klauk followed his 64 with a 69 to get to seven-under having bogeyed his penultimate hole, the par-four eighth.
That left Klauk two shots off the lead and alongside fellow Americans Chris Riley, who hit a second-round 66 that included three birdies in his last four holes, and Kris Blanks, who fired a seven-under 63 for the low round of the day.
Tied for fifth on six-under were Americans Kevin Na, Marc Turnesa and Steve Flesch, all having shot 65s while veterans Jeff Sluman and Jeff Maggert were among a six-man group on five-under at halfway.
Mathias Gronberg and Jesper Parnevik of Sweden and England's Brian Davis ensured there would be a European presence in Wisconsin going into the weekend.
All shot second-round 68s, Gronberg moving to level-par for the tournament, Davis and Parnevik getting to one-over, right on the midway cut line.