Brian Gay was tied with Hart on the back nine Thursday, but missed a 12-foot par try at his 17th hole, which cost him a piece of first place.
Instead, Gay is tied for second place with 2001 PGA Champion David Toms, American Ryder Cup captain Paul Azinger, Tom Pernice, Jr., John Rollins and Aaron Baddeley at 6-under-par 65.
Hart began on the back nine Thursday and collected his first birdie at the par-5 13th. He hit a terrible second shot, but chipped to 10 feet and converted the birdie putt. Hart missed the fairway left at the 14th, but hit a 5-iron 12 feet short of the flag to set up his second consecutive birdie.
At the par-5 15th, Hart laid up short with his second, but did not put his ball in a good position. He found a bunker and was unable to get up and down to save par.
'You look at it and say how in the heck did you bogey that hole? You'd be amazed what you can do if you play this game long enough,' said Hart. 'You can do all kinds of things.'
That would be the only miscue of the round for Hart. At the par-3 16th, Hart knocked a 6-iron to 30 feet and rolled in the long birdie putt. He made it two in a row thanks to a 10-footer at the 17th and was out in 3-under 33.
Hart parred No. 1, then went on a birdie run from the second. Hart holed a 20- footer for birdie at two, then sank an 8-footer for birdie at three. He polished off three in a row when his 7-iron approach at the fourth stopped 4 feet from the cup.
Hart had one more great shot left in his round. At the par-4 eighth, Hart drove into the fairway, then hit a spectacular 6-iron that came to rest 3 feet from the hole. Hart tapped in the birdie effort to grab sole possession of the lead.
'I hit a lot of good mid to short irons, gave myself a lot of good birdie opportunities and obviously putted pretty well,' said Hart, a two-time winner on the PGA TOUR, with his last win coming at the 2000 Honda Classic. 'You make eight birdies, you've got to be making some putts. So I putted pretty well.'
Gay reached 7 under par thanks to eight birdies and a bogey through 13 holes. He teed off on the back nine in round one so his 14th was No. 5 and he had a birdie chance there from 20 feet. Gay missed that one and it started a tough stretch for the American.
He missed a 9-foot birdie putt at the sixth, then a slightly longer birdie try at the very next hole. Gay's 12-foot par putt at the eighth stayed above ground, but Gay had one more look at matching Hart atop the leaderboard. Hart failed on a 10-foot birdie effort at his last to stay one behind.
'I had some chances coming in but didn't make any putts the last five holes or so, but played really solid,' said Gay. 'I'm really happy to get off to a good start.'
Billy Mayfair, Bart Bryant, Daniel Chopra, Bubba Watson, Robert Garrigus and former U.S. Amateur Champion Jeff Quinney, who has two top-10 finishes in his last two starts, are knotted in eighth place at 5-under-par 66.
Reigning Masters champion and two-time winner of this event Phil Mickelson continued struggling this season. He opened with a 1-over 72 and is part of a tie for 88th place.
'It wasn't a very good round,' acknowledged Mickelson, who has tied for 45th and 51st in his two starts in 2007. 'I made a number of bogeys and made some good birdies, but just didn't get it under par. There were a lot of low rounds out there. Even though the weather wasn't the best, there were still a lot of birdies to be made. I just made too many mistakes.'
Defending champion J.B. Holmes was worse than Mickelson on Thursday. He only managed a 3-over-par 74 and is tied for 117th place.