Jesper Parnevik (68), Camilo Villegas (64), Arron Oberholser (68) and Jonathan Byrd (68) are knotted in first place through 36 holes. They stand at 7-under-par 133 and nine players, including overnight co-leaders Jim Furyk and Justin Rose, are only one shot behind.
The Swede, a five-time winner on the PGA TOUR who has not visited the winner's circle since 2001, started on the back nine Friday and flew out of the gate with birdies at 11 and 12.
From there, Parnevik valiantly battled windy conditions that featured gusts up to 30 miles per hour. He parred the next eight holes around the turn, but found trouble at the third.
Parnevik elected to hit driver and left himself with a sand-wedge approach. He hit a poor shot and walked off with a bogey. It took the former Ryder Cupper six holes to reclaim the lost stroke as he closed with a 9-foot birdie putt to grab his share of first.
'I'm happy playing the way I am now,' said Parnevik. 'This is a very tough golf course to start with. When you get winds like this, it's tough to figure out which direction the wind is coming from.'
Villegas, a PGA TOUR rookie, struggled early on Friday. He hit a terrible drive at one, then missed a 7-footer to save par. That would be the final mistake for the Colombian.
He birdied the second and fourth, then rolled in a 5-footer for birdie at No. 5. Villegas parred his next four holes to make the turn at 2-under-par 33.
Villegas parred the 10th, then hit two poor shots at the 11th. Luckily, he hit one good one, a chip-in birdie from 30 feet. Villegas made it back-to-back birdies with a 15-footer at the 12th.
On the 15th, Villegas sank a 60-footer for birdie and at 17, the rookie canned a 14-foot birdie putt to join the logjam atop the leaderboard.
'It wasn't easy out there, I can tell you,' said Villegas. 'It was gusting. I managed to roll some great putts. That makes up for it. Just got to keep doing what I'm doing.'
Oberholser, whose only win on TOUR came this year at Pebble Beach, teed off 10 first and rolled in a 12-foot birdie putt. He added another birdie on his opening nine when he knocked a pitching-wedge to 15 feet at the 14th.
On the second nine, Oberholser reached 8 under par thanks to a lob-wedge approach that landed 10 feet from the hole. Eight-under would be short-lived as Oberholser gave one back at the sixth, a hole he has bogeyed each of the first two rounds.
'I don't have a club for that hole,' admitted Oberholser. 'Five-wood is too much and 3-iron is not enough. Tomorrow, we're just laying up. I didn't bring all of the tools.'
Byrd was actually 1 over par with three to go, thanks to three bogeys and two birdies.
At the par-4 seventh, his 16th, Byrd ran home a 15-foot birdie putt to get to 5 under par for the championship. He holed a birdie putt from the same distance at eight, then converted a 9-foot birdie putt at his last to join the group at minus-7.
'Today was kind of a struggle all day,' acknowledged Byrd. 'It was windy and I was just kind of scraping it, making good pars. I made a couple of putts and made a couple of birdies.
Both Furyk and Rose struggled to rounds of 1-over 71. They were joined in fifth place by reigning Rookie of the Year Sean O'Hair (69), Nathan Green (70), Trevor Immelman (66), Tom Pernice, Jr. (68), Brett Quigley (63), Ryuji Imada (68) and Eric Axley (66). That group is at 6-under-par 134.
Former British Open champion Ben Curtis (66) and Brian Davis (68) are a shot back at minus-5.
Defending champion Mark Calcavecchia posted a 4-over-par 74 on Friday, but it was enough to make the weekend. He finished 36 hole on the cut line at even-par 140.