Steve Lowery collected 13 points with seven birdies and a bogey and built a four-point lead after the second round of The International in Colorado.
The $4.5million USPGA tournament uses the modified Stableford scoring system.
Lowery's second-round total was the second-highest behind Mark Brooks, who had nine birdies and four bogeys to score 15 points to climb 58 spots into third place with 15.
Craig Barlow had 10 points after six birdies and two bogeys and is alone in second with 17 points, three ahead of The Open champion Ernie Els, who won this event in 2000.
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First-round leader Steve Pate never got going in the second round and remained stuck on 11 points, sliding into a tie for fifth.