Morris Hatalsky, who shared the opening-round lead with Thorpe, posted a 65 to finish in second place at 12-under-par 128. Craig Stadler matched the record for lowest 18-hole score in Champions Tour history with a 60 in the second round to vault into third place at 11-under-par 129.
'I drove the ball better today than yesterday,' said Stadler. 'Made a lot of putts today. You have to do that to go low.'
Thorpe, who won his last start at the FedEx Kinko's Classic, was part of a three-way tie after the first round but found himself looking up at Stadler when he teed off on Saturday at The Moors Golf Club. Thorpe started well with a pair of birdies over his first four holes but stumbled to a bogey at the fifth.
He parred his next five holes and moved to 9 under with a birdie at the par-5 11th. Thorpe then birdied the par-4 13th and grabbed a share of first with a birdie at the par-4 14th.
At the par-4 15th, Thorpe played his approach inside 3 feet and rolled in the short birdie putt to take the outright lead. Thorpe missed the green at the par-3 16th but chipped in for another birdie to make it four in a row. He parred his way in to hold onto the 36-hole lead.
Hatalsky birdied the second and the fourth to reach 9 under. He joined Stadler in the lead with an eagle at the par-5 seventh but gave a shot back with a bogey at the ninth.
The 53-year-old returned to the top of the leaderboard with a birdie at the par-5 11th. After Thorpe made his move on the back nine, Hatalsky hit his second shot within a foot of the hole at the 18th to finish one shot back.
Stadler opened his round with a birdie at the first and ran home a 40-foot putt for a birdie at the second. He then hit a wedge to 4 feet for a birdie at the fourth and added back-to-back birdies starting at the par-4 sixth.
He struggled to a bogey at the ninth but recovered with three straight birdies from the 10th. Stadler added a birdie at the 14th and had the 59 in sight after he picked up birdies at the 16th and 17th holes.
Stadler had another birdie chance at the last but his putt died to the right.
'It looked like it had a chance all the way down,' Stadler said of his putt at the 18th. 'I've never had a chance at 59 before.'
Defending champion Tom Jenkins posted a 65 to join Dana Quigley, Dick Mast, David Eger, Hugh Baiocchi and Mike Sullivan at 9-under-par 131.