Robert Allenby, the 2001 winner, shot a 4-under 67 and is in the clubhouse at 6-under-par 136. Kevin Sutherland is 6 under par through four holes and first-round leader Brian Davis did not hit a single shot on Friday, but remained in a tie for second place.
A four-hour storm delay hampered the tournament on Friday. The group with the early tee times in the second round finished, but the other half of the field will return to Riviera at 10:30 a.m. ET Saturday morning.
The hope is that the second round will be completed Saturday, then the 36-hole cut can be made. Tournament officials said that the third round will hopefully begin shortly after the completion of the second with players in threesomes off both the first and 10th tees.
Unfortunately rain is scheduled for the weekend at Riviera, making a Monday finish a possibility. The problem with the tournament ending on Monday is that next week is the World Golf Championships - Accenture Match Play Championship, which begins on Wednesday.
'That will be tough,' admitted Allenby. 'I don't care. I'm happy to play Monday. If I've got a chance to win the tournament on Monday, I will be more than happy to be here on Monday.'
Tiger Woods, who can regain the No. 1 ranking in the world with a solo fourth or better this week, is 5 under par through four holes and tied for fifth place.
Luke Donald (71), Stephen Leaney (67) and Rocco Mediate (67) completed their second rounds at 5-under-par 137. Darren Clarke is 5 under through six holes and Adam Scott is also at minus-5 after five holes.
They will all be chasing Campbell, a two-time winner on the PGA Tour and American Ryder Cupper. He opened on the back nine Friday and wasted little time in breaking into red figures.
At the short, par-4 10th, Campbell drove short of the green and chipped up to tap-in range. He made it back-to-back birdies at the par-5 11th when he went driver-three-wood-sand-wedge and converted a 3-footer.
Campbell, considered by his peers to be one of the best ball-strikers on tour, hit a 7-iron to a foot to set up birdie at the par-3 16th. He made the turn at 3-under 33 and in first place.
His playing partner James Driscoll took the lead at 7 under with a tap-in eagle at the par-5 first. Campbell matched him in first at the same hole when his second came up short of the putting surface and he chipped 12 feet past the cup. Campbell stroked home the birdie to reach minus-7.
Campbell nearly made bogey at the par-3 fourth as he came up short of the green. He chipped to 12 feet and converted the par putt to keep his round going.
At the fifth, Campbell knocked a 6-iron to 8 feet to set up his fifth birdie of the round. He collected No. 6 on the sixth when he rolled home an 18-footer from the fringe.
Campbell parred out to polish off his 65.
'I played real good,' said Campbell. 'I honestly thought we wouldn't even start today. The course was great though. It was nice to see the ball go in the hole.'
Campbell's victories came at some impressive events, the 2003 Tour Championship and last year's Bay Hill Invitational. He would love to add this title come Sunday. Or Monday.
'I really worked hard last week when I was at home,' said Campbell. 'I love coming to this tournament. It's one of my favorites and I love the course. Starting off in a good state of mind always helps.'
Two-time defending champion Mike Weir was near the top of the leaderboard throughout much of Friday's round, but one bad hole ruined his day.
At the 13th, Weir hit his approach long, then three-putted from inside 7 feet. He left the hole with a triple-bogey 7, en route to a 2-over 73. He is tied for 33rd place at 2-under-par 140.