Johnson Wagner, aiming for his first PGA Tour victory, shot a three-under-par 69 to take a one-stroke lead over fellow American Chad Campbell after the Houston Open third round.
Wagner, ranked 313th in the world, finished with a 15-under total of 201 as he chased the first prize of $1 million and a win that would earn a spot in next week's US Masters field at Augusta.
Campbell, wielding a hot putter, was tied for the lead before a bogey at the par-four 17th prevented him registering a second successive 64. His 65 put him on 202 at the Redstone Golf Club.
Americans Bob Estes, who fired a bogey-free 64, and Charley Hoffman (69) were tied for third on 204.
None of the top four have yet qualified for the Masters, the year's first major.
Geoff Ogilvy, the 2006 US Open champion, posted a 66 for 206 while fellow Australian Mathew Goggin carded a 72 for 207.
Thirty-six players returned early on Saturday to complete the second round which was suspended due to a long weather delay on Friday.
Holder Adam Scott of Australia, who complained of feeling ill during the week, added a second-round 69 to his course-record opening 63 but withdrew before the third round because of fever and swollen glands.
American Davis Love III, needing a win here to join the Masters field and keep alive his streak of playing in 70 successive majors dating back to the 1990 British Open, was six under on 210.
