John Huston is alone in fifth place at 7-under-par, followed by Carl Paulson, Pat Bates and Lee Porter, who share sixth at minus 6.
Gamez is as unlikely a co-leader as one could imagine. He has not cracked the top-10 on the PGA Tour since a fifth-place tie in the 1997 B.C. Open, and his best finish last season was a pair of 11th-place ties.
Gamez burst on to the scene in his rookie campaign in 1990. His first victory came in his first PGA Tour event at the Tucson Open, besting Calcavecchia by four strokes. He followed that victory later in the year with a dramatic win at Bay Hill, where he holed a 7-iron from the fairway at the 72nd hole to capture the title by one stroke over Greg Norman.
'I said this week that I was going to come out and fire at it and see what happened,' said Gamez, who entered the field this week as the seventh alternate. 'That's the way I've always played in junior golf and college golf and the first four or five years out here.'
Gamez was 1-under after his front nine but caught fire on the back. He birdied four holes in a row from the 13th and held on to his piece of the lead with a 30-foot par save at No. 17.
Gamez's closest competitors are not surprised that the former Rookie of the Year is at the top of his form once again.
'He's still a heck of a player,' said Calcavecchia, who shot a 3-under 69 Friday. 'Everybody goes through tough times in their career and he's been having a tough time for the last five or six years. That doesn't mean he can't play.'
'Robert has always been good, he just didn't know it,' Mediate said. 'Whatever it was in 1990 that was in there, it's still in there. He's got to figure a way to get it out. It looks like he's figured that out this week. This guy was all-world in 1990.'
Gamez, who hasn't led after 36 holes since he shared the halfway lead with Ben Crenshaw at the 1995 Memorial, admits that he will carry some nerves into Saturday's final pairing.
'I'm going to be nervous, I was nervous on the last few holes coming in today,' said Gamez, who has earned less than $10,000 in three events in 2002. 'But it's a good nervous. It's good to have those butterflies. I haven't had those in a long time.'
Calcavecchia broke out early with a birdie and an eagle in his first six holes but dropped a shot at his ninth, No. 18 at Forest Oaks Country Club. He ran home a 10-foot birdie at the seventh to reach 10-under par.
'I had a lot more birdie chances yesterday,' said Calcavecchia. 'I just didn't have that many chances to roll in any birdie putts. I was basically struggling for pars a lot of the time.'
Michael Allen, Jay Haas, Bob Heintz, Chad Campbell, Jerry Kelly and WGC-Match Play champion Kevin Sutherland share ninth place at 5-under-par 139.
John Maginnes needed only 19 putts Friday, one more than the PGA Tour record for fewest putts in a round. He two-putted from 20 feet at 18 to miss matching the record but posted a 2-under 70 to tie for 43rd at minus 2.
Bubba Dickerson, the reigning U.S. Amateur champion making his professional debut this week, struggled to a 77 Friday. He missed the 36-hole cut, which fell at even-par 144, by six strokes.
Full-field scores from the Greater Greensboro Chrysler Classic