Craig Stadler and David Edwards, who each shared the first-round lead with Fleisher and three others, both shot 70 in round two. They share second place at minus-6.
Des Smyth made a mess of the 18th hole Saturday as his closing double-bogey dropped him to 5-under-par 130 after a 69. He stands alongside another first-round co-leader, Tom Kite (71), in fourth.
Jay Haas, the fifth of six first-round co-leaders, managed an even-par 72. He was joined in sixth place at The Hills Country Club by Bob Gilder and Mark James.
Fleisher tumbled out of a share of the lead right off the bat Saturday as he bogeyed each of the first two holes. However, his five-iron tee shot at the par-three third found the bottom of the cup for a hole-in-one that got him back to minus-four overall. That was his fourth ace in his Champions Tour career.
'You start bogey-bogey, its not a good day. But when you make a hole-in-one, it changes things,' Fleisher said. 'I was just a tough day overall.'
The 18-time winner on the Champions Tour steadied himself with five straight pars. He kicked in a 3-foot birdie try on the ninth to get to minus-5, three behind Smyth.
Fleisher moved to 2-under for his round with a birdie on the 12th. A bogey on 13 by Smyth, who fell to minus-7 with the miscue, meant Fleisher was within one of the lead.
The 57-year-old Fleisher parred four straight before sinking a 5-foot birdie putt on the 17th got him to minus-7 and he parred the last.
'It is getting more and more difficult to win out here,' said Fleisher, whose last win was at the 2004 Bruno's Memorial Classic. 'I feel fortunate to be in this position, but there is a lot of golf left.'
Stadler, who fought a balky putter all day, managed two lone birdies on the fourth and 11th. He parred the other 16 holes to share second.
'I left a few out there today,' Stadler admitted. 'I putted well on Friday, but didn't putt well today. I missed a lot of short putts. You can't afford to give a lot of those putts away like I did.'
Edwards grabbed the lead early on at minus-six as he eagled the par-five second. However, he gave one stroke back with a bogey on the fourth. The 50- year-old wrapped birdies on the eighth and 10th around a bogey on No. 9. Edwards ran off eight consecutive pars to close out the round.
Smyth birdied each of the first three holes to jump to minus-five. He claimed the lead with a birdie at the sixth. The Irishman pulled two clear of the field with birdies on eight and 10.
However, his lead fell to one after his bogey on 13. At the last, Smyth found a hazard off the tee. He took five shots to reach the putting surface at the par-five last. He two-putted for double-bogey to fall to minus-five. He ended on No. 9 Friday and also double-bogeyed that hole.
Tom Jenkins carded a two-under 70 Saturday to get to three-under-par 141, where he is alone in ninth. Curtis Strange, the last of the first-round leaders, struggled to a two-over 74. He shares 10th with defending champion Jim Thorpe (70) at two-under-par 142.
Hale Irwin, the 2003 champion, stands alongside Jose Maria Canizares, Pat McGowan and Don Pooley as the final players in red figures at minus-one.