Ted Purdy shot a 4-under 67 in the second round and is alone in third place at 6-under-par 136.
Darren Clarke (66), Jay Haas (69), Kevin Na (68), Patrick Sheehan (66) and John Huston (68) share fourth place at 5-under-par 137.
Curtis, who took home the Claret jug last year at Royal St. George's, opened on the back nine Friday. He parred his first five holes, then netted his first chip-in birdie, from 25 feet, at the par-5 15th.
The reigning British Open champion played more spectacular golf after he made the turn at Harbour Town. He holed his second shot with a sand-wedge from 110 yards for an eagle-2 at the first hole and made an 8-footer to get up and down from a bunker for birdie at two.
At the third, Curtis drove well right of the fairway. He pitched out short of the green then collected his third hole-out, this time a bump-and-run from 50 feet.
'I played very well today,' said Curtis. 'I didn't hit very many good drives but I hit good iron shots and had key ups and downs and holed some good shots. Three zero putts. I haven't had three zero putts in a month.'
It has been nine months since Curtis shocked the golf world. Since the magical win at the British Open, Curtis has only held the lead once on the PGA Tour, after the first round of the WGC-NEC Invitational. That coincided with the week of his wedding, but Curtis now may be ready to validate his major win.
'You've got to put that aside, that's done and over with,' said Curtis. 'I know I'm the Open champion, but at the same time you have to look past it and look to the future, not always rely on the past. I feel good about the game.'
Slocum, the winner of this year's Chrysler Classic of Tucson, played in the afternoon session and like Curtis, started on the second nine. He broke into red figures quickly with a 6-footer for birdie at the 10th, then five holes later made a putt of similar length for his second birdie of the round.
He dropped a shot at the par-3 17th when he landed in a bunker but made up for the miscue around the turn. Slocum, a three-time winner on the Nationwide Tour, sank a 25-foot birdie putt at the first, then added a 4-foot birdie putt at the second to reach 6 under par for the championship.
Slocum played a spectacular 2-iron to 6 feet at the par-5 fifth. He missed the eagle putt but tapped in for birdie to get within one of Curtis' lead.
At the ninth, his last, Slocum had 10 feet for birdie. He misread the putt and missed a chance at sharing the 36-hole lead, which would have been the second time on tour after his victory in Tucson.
Besides Slocum's newfound success this year on tour, Slocum also has some history in this event. He finished second to Justin Leonard by a stroke in 2002.
'You can draw on those experiences from Tucson to last year or two years ago when I played well here, just go out and really just try to focus on my game,' said Slocum. 'I generally play a lot better when I do that.'
Bay Hill winner Chad Campbell (69), two-time major winner Mark O'Meara (67), Scott Hoch (68), Stephen Ames (68) and Fred Funk (69) are knotted in ninth at minus-4.
First-round leader Cameron Beckman managed a 1-over 72 and is part of a group in 14th place at 3-under-par 139.
Defending champion and five-time winner of this event Davis Love III carded a 1-under 71 on Friday and is in a logjam tied for 38th. He is currently at even-par 142.
The 36-hole cut fell at 2-over-par 144 and among the notable players who will not be around on the weekend are: Jeff Sluman (145), Retief Goosen (148) and Lee Westwood (153).