Chad Campbell held the clubhouse lead in the HP Byron Nelson Championship in Texas after shooting a second-round 66.
The American moved to six under par at the halfway point, but sat one shot adrift of Dicky Pride, who was seven under overall after 13 holes.
Campbell picked up four birdies in a bogey-free round as he added to his opening 68.
Pride was three under for his round so far with four birdies and a bogey.
Two more Americans, Matt Kuchar and Keegan Bradley, were out on the course on six under, with both having played 16 holes.
Kuchar was two under for the day thanks to a topsy-turvy round featuring six birdies, two bogeys and a double bogey.
Bradley was three under with six birdies and three bogeys.
Overnight leader and Texas native Ryan Palmer dropped back to five under overall through 17.
He was one over for the day following two birdies and three bogeys.
