One of two overnight co-leaders, Johnson is clinging to a one-shot lead at 15- under 201 after posting five birdies and two bogeys in the third round.
Sunday, he will be seeking his third Nationwide Tour win and first since 2000.
'Not a bad spot to be,' said Johnson, who is one of the top-ranked players on tour without a win this season. 'There are some good players up there with me, too. If I play good tomorrow, I've got a chance.'
Brad Elder fired a 6-under 66 and climbed five places into a tie for second alongside Jon Turcott (68) and Jason Day (69) at 14-under 202.
Day, the 19-year-old Australian star, finished his round birdie-eagle to get within one of Johnson.
Kyle Thompson (67) and Roland Thatcher (67) were two shots further back at 204.
It was the third time in two years that Johnson held the 54-hole lead on the Nationwide Tour. The previous two times -- at the 2006 and '07 BMW Charity Pro-Am at the Cliffs -- he didn't manage to come away with a win.
Winning is something he hasn't done since it was called the Buy.com Tour, although Johnson has made a habit of posting good finishes this season. He had two runner-up finishes in his last four starts and has posted five top-10s on the season.
He was within sight of a win just last month.
Johnson held a one-shot lead heading to the 17th hole in the final round of the Northeast Pennsylvania Classic, but he knocked his approach shot into a creek near the green and made double bogey to finish second.
It's something he's in no hurry to repeat this week. But with the leaderboard as tight as it is, is might not take a big mistake Sunday to lose the lead.
At the end of Saturday's third round, there were 12 players within five shots of Johnson's lead, leaving the prospects of an exciting Sunday at Shadow Hills Country Club a near certainty.
'They are going to come after me,' said Johnson, 'but it's better to be in this situation than five strokes back.'