The first three rounds of the event were spread over three courses - the par-72 The Cliffs Golf & Country Club (Cliffs Valley), the par-71 The Cliffs at Keowee Vineyards and the par-71 The Cliffs at Walnut Cove. Sunday's final round will be staged at the Cliffs Valley course.
Kevin Stadler (68), Jess Daley (67), Ken Duke (68) and overnight leader Chris Stroud (71) are knotted in second place at 9-under-par 205. Scott Weatherly managed an even-par 71 at Walnut Cove and is alone in sixth place at minus-8.
Johnson began on the back nine Saturday and hit a poor drive at his opening hole. Luckily, he got a wedge on the ball and knocked his approach close to set up a birdie.
He parred his next six holes, then reached the green in two with a 4-iron at the par-5 17th. Johnson two-putted to make the turn at 2-under-par 33 for his round and minus-8 for the championship.
On the second nine, Johnson wasted little time in breaking into red figures. He hit a 4-iron to 25 feet and converted the birdie putt at the first hole.
Johnson continued his fine play at the par-5 sixth as, once again, he reached the putting surface with a 4-iron second shot. He could not convert the eagle try, but settled for a birdie to reach 10 under par.
That score did not last long as he bogeyed No. 7. Johnson reached the par-5 eighth green with a 3-wood and two-putted for another birdie. At the ninth, Johnson holed a clutch par save to keep sole possession of the spot atop the leaderboard.
'I played pretty good today,' acknowledged Johnson, a two-time winner on the Nationwide Tour. 'I hit it solid all day. I made birdies when I needed to. Hopefully I'll be able to sink a few putts tomorrow.'
Johnson has not held the 54-hole lead in a Nationwide Tour event since the 2000 Ozarks Open. He has not won on the circuit since the Monterey Peninsula Classic of the same year, but Johnson is not all that shocked to be sitting in the lead.
'It doesn't surprise me,' said Johnson. 'Tee to green I've been solid all week, but I haven't gotten anything out of my game. Today I was able to take advantage of some opportunities and I went pretty low.'
Stadler got his round off to a great start with a tap-in birdie at the first at the Cliffs Valley course. He notched back-to-back birdies from the seventh and rolled in a 15-footer for birdie at 17 to get within one of the lead.
'I'm not hitting it great, but I'm making a bunch of pars,' said Stadler, who won on the European Tour earlier this season. 'I didn't expect to do much this week. I'm just not confident.'
The three players Stadler shares second with all played the Walnut Cove course and began on the back nine.
Daley mixed six birdies and two bogeys, while Stroud tallied three birdies and three bogeys. Duke recorded four birdies and a single bogey.
Chez Reavie, Matt Weibring and Jason Buha all shot 68s on Saturday and are tied for seventh place at minus-7.
The 54-hole cut fell at 1-under-par 213 with 74 players advancing to Sunday.