Whether he remained atop the leaderboard depended on Padraig Harrington, Phil Mickelson and others who played under warm sunshine in the afternoon.
But it was another impressive round by Howell in a season that so far is loaded with progress. He already has two runner-up finishes, at the Sony Open and Buick Invitational, and is starting to believe a long-sought victory might be around the corner.
"The best thing I can do is keep giving myself chances," said Howell, who was at 8-under 134.
David Howell of England birdied his final hole for a 68 and was at 135 along with Sergio Garcia (68) and Pat Perez (69). Another shot back was Rocco Mediate, playing on a medical exemption this year. He shot 66 and was among those at 137.
Howell, the 27-year-old American, has had nine runner-up finishes since his lone PGA Tour victory in 2002. One that stung the most came four years ago at the Nissan Open when he had a three-shot lead going into the final round and lost on the second playoff hole against Mike Weir.
The turning point Friday came around the turn.
Howell started his round at No. 10, and he was 2 under for the day when he approached the par-5 17th. He realized he would be playing two par 5s (No. 1 is the easiest at Riviera), a chance to make up ground.
"Riviera is an interesting golf course," he said. "There's a few birdie holes out here, and then all of a sudden you have a run of a few holes were par is a good score. So playing holes No. 17 and No. 1, you really have to make birdie on those holes."
He laid up on the 17th and hit sand wedge to a 6 feet for birdie. On the first hole, he easily reached in two with a 4-iron and two-putted from about 50 feet. But he also picked up birdies on both ends of those par 5s, hitting 8-iron to 15 feet on the uphill 18th, and hitting a good drive and an 8-iron into 10 feet on No. 2.
Howell then reached the stretch where par is a good score, and he was good the rest of the way.
Garcia, among several international players making his PGA Tour debut at Riviera, finished strong. He traded birdies and bogeys most of the round until sticking his tee shot within 2 feet on the par-3 14th, holing a 10-foot birdie on the par-3 16th and chipping in on the 17th with a shot that quickly changed his mood.
He laid up on the par 5, but hung out his wedge to the right rough. But when the chip banged off the pin and disappeared into the hole, the Spaniard was all smiles.
"I just thought, 'What the hell? Why don't you just chip this in?'" he said. "And it worked out."
He had a chance to tie for the lead until missing an 8-foot birdie putt on the 18th.
U.S. Open champion Geoff Ogilvy and former British Open champion Ben Curtis were among those at 4-under 138, while former Ryder Cup captain Tom Lehman finally showed signs of life with a 66 that put him in the group at 139.