James Driscoll shot the best round of the day to establish a one-stroke lead at the end of the second round of the Puerto Rico Open in Rio Grande.
The American followed up his opening-day 69 with a nine-under-par 63 to improve to 12-under overall.
Driscoll was able to sign a blemish-free card showing seven birdies and an eagle at the par-five fifth.
The 36-year-old is just ahead of compatriot Chesson Hadley, who opened with a 68 and improved to 11-under thanks to a 65 on Friday.
"I had the putter going pretty hot today," Driscoll said. "I was fortunate. I hit a bunch of shots pretty close, too. I judged the wind.
"Luckily, I read the wind right a couple of times. The wind was pumping pretty good. It was blowing about 20 miles an hour, but there were a few times I had some crosswinds and just judged it perfectly and hit it in there to about a foot or so."
Eric Axley (66) was alone in third place on 10 under, with Ben Martin, Wes Roac, Jonathan Byrd and Danny Lee tied for fourth a stroke back.
Axley said: "I'm playing solid, hitting a lot of greens right now, being patient, and getting a lot of them close to the hole. So putting's not been too difficult.
"It's a little soft right now, after the rain we've had. Yesterday, when we played it was kind of getting a little firmer. If the wind blows a little and no more rain, it could get a little firmer for the weekend."
David Toms enjoyed the second-best round of the day, his 64 moving him level with a host of players on eight under, among them Ricky Barnes and Englishman Greg Owen.