Lucas Glover stretched his lead to two strokes on the third day of the Zurich Classic.
The American produced his worst round of the week, a two-under 70, but it was still enough for 14 under overall and a two-shot advantage over a group of four men led by a surging Kyle Stanley.
"It got a little tougher this afternoon," Glover, looking for his first win in two years, told www.pgatour.com. "I didn't play the way I wanted coming in, but it's always good to get one (a birdie) on the last.
"I'm where I wanted to be starting the day."
Glover carded five birdies against three bogeys and his round was highlighted by a bunker shot at the second which took him to within a couple of feet.
But it was Stanley who really caught the eye as his seven-under 65 put him level with Jimmy Walker, Billy Horschel and DA Points on 12 under.
Stanley set the tone by going eagle-birdie on the second and third and, though he dropped a shot at the fifth, another five birdies saw him climb the leaderboard.
Walker and Horschel were almost as good, each carding a 66 - Horschel's was bogey-free - while a number of other players went low to put themselves in contention.
Kevin Stadler fired a 65 to sit alone in sixth on 11 under, while Henrik Norlander did likewise for a share of seventh at 10 under alongside first-round leader Ricky Barnes, whose 66 today was closer to his opening round of 64 than his second circuit, a 76.