D.A. Weibring moved from a share of third to sole possession of second place with his second straight round of 4-under 68. His 8-under-par total of 136 is one stroke clear of Jay Sigel, Hale Irwin and defending champion Tom Jenkins.
Fleisher got his round going with a birdie at the par-5 fifth on the Founder's Course at Greystone Golf & Country Club. However, he stumbled to a bogey at the par-3 seventh, his first bogey of the event.
Fleisher, who was runner-up here last year, came back with a birdie at the ninth to get back to minus-9.
Around the turn, Fleisher rolled home back-to-back birdies from the 11th to move to 11 under and three shots clear of the field.
He rolled off five straight pars. Then at the last, Fleisher spun his third shot back within inches of the cup for a kick-in birdie at the par-5 18th to take a four-shot cushion into the final round.
'That's a nice way to finish,' said Fleisher. 'Four shots, that's a nice lead. But I don't think anybody's real confident, not with who you've got behind you. We'll see.'
Weibring picked up a birdie at the third, but stumbled to a bogey at the very next hole. He erased that mistake with a birdie at the sixth and capped his opening nine with another birdie at the ninth.
The reigning SAS Championship winner converted back-to-back birdies from the 12th for the second straight round. He briefly climbed to minus-9 with a birdie at the 15th. Weibring, however, stumbled to a bogey at the last to slide back to minus-8.
'I was thinking about a rainout,' said Weibring of Sunday's forecasted rain. 'I was trying to be aggressive and I was just very disappointed in myself. I was not focused in on that tee shot on No. 18. I played that hole very poorly, but my caddie said it was the only one I've played poorly out of 36 so far.'
Jenkins fought from a tie for 25th to a share of third with a solid back nine. He picked up birdies at the second and sixth to get to minus-3. He tripped to his lone bogey at the seventh, but came back to birdie the ninth.
'At that point, I was a little bit discouraged,' said Jenkins of his bogey at the seventh. 'It probably got me focusing more on the round.'
Jenkins, who is attempting to become the first two-time winner of this event, ran off four consecutive birdies from the 11th to vault into a share of third place.
Dave Eichelberger and Larry Nelson, who each posted rounds of 2-under 70, share sixth place at 6-under-par 138. Des Smyth, Lee Trevino and Graham Marsh are one stroke further back at minus-5.
Doug Tewell, Wayne Levi, Bruce Lietzke, Raymond Floyd, Bob Murphy and Dana Quigley share 11th place at 4-under-par 140.