Ricky Barnes saw a six-stroke lead at the turn pegged back in the third round of the US Open at Bethpage Black.
Barnes bogeyed on 18 to drop to eight-under 202, only one stroke ahead of compatriot Lucas Glover.
The pair each fired third-round level-par 70s.
Barnes had five bogeys in his last 12 holes, but still feels that he is right in the hunt.
"I'm in good position," Barnes said. "I shot even par at the US Open. If I go out and do the same thing again, someone's going to have to go really hard to catch me."
Phil Mickelson sank a 25-foot birdie putt on the 18th hole on Sunday to complete a one-under par 69 third round which moves him into contention.
The 39-year-old American left-hander fired seven birdies, four bogeys and a double bogey in a topsy-turvy 18 holes.
"If I can get a hot round going I can make up the difference. I'm one good round away," Mickelson said.
"I'm making enough birdies to shoot 5- or 6-under. I feel like I'm only 18 good holes away."
England's Ross Fisher and David Duval shared third place on 207 with Mickelson, Hunter Mahan and Canada's Mike Weir a shot behind on 208.
Defending champion Tiger Woods fired a two-under 68 to share 15th place on 211, nine off the lead.
"You have to play a great round of golf and get some help," Woods said. "It is out of my control. All I can control is whether I play a good round or not."