Tom Carter, Scott Dunlap and Kelly Gibson each shot rounds of 66 to move to 8-under-par 205. They were joined by Andy Sanders, who had a third-round 67, in a tie for third.
'This is my first experience with the Nationwide Tour,' said Bohn. 'I don't really look at it as a lead, you only have a lead if you're up five or six shots.'
After a sizzling 65 on Friday that moved him into a share of the lead with Allen, Bohn jumped out of the gate with back-to-back birdies starting at the par-4 second.
He found trouble with a bogey at the fourth but countered quickly with a birdie at the very next hole en route to a 33 on the front nine at DiamondBack Golf Club.
Bohn reached 10-under with a birdie at the par-5 11th and pulled three shots clear of the field with a birdie at the par-4 14th.
Bohn's round seemed to come apart shortly thereafter with a pair of bogeys from the 15th but he managed a birdie at the last to secure sole possession of first with one round to play.
'That was a great up-and-down on the last hole,' said Bohn. 'I got a little shaky on 15 and 16 so it was a nice one to get back.
'You've got to fire at the flag sticks out here. Like the commercial says 'These Guys are Good.' I'm going to have a lot of fun tomorrow. I have nothing to lose and everything to gain.'
Allen had a solid outward half with three birdies and one bogey to make the turn at nine-under. He stumbled with a bogey at the 10th but stayed within reach.
At the par-5 last, Allen tallied a closing 25-foot birdie to break a logjam at 8-under par and move into second place alone.
'To get in the last group is nice,' Allen said. 'I think I have a good chance tomorrow. To win the tournament would show I am getting close.'
Zach Johnson fired a 5-under 66 to finish four shots off the lead alongside Danny Briggs and P.J. Cowan at 6-under-par 207.
Blaine McCallister, Michael Long, Steve Ford, Terry Hatch, Derek Gillespie and Kevin Muncrief were one shot further back at 5-under-par 208.