Thorpe, who has finished higher than sixth in just one of 19 Senior PGA Tour events this year, shot a 6-under-par 65 and pulled within a shot of Bruce Fleisher at 134 after two rounds in the U.S. Senior Open.
"The golf course fits the way I play," Thorpe said after shooting what he said was the best nine holes of his life.
Thorpe birdied the last three holes for a 30 on the back nine at Saucon Valley Country Club. He matched the record for lowest nine-hole score previously posted by five players, most recently by Ed Dougherty on the back nine of the first round last year.
Thorpe, 51, pumped his fist after sinking a long birdie on the 18th hole as an ever-growing gallery roared.
He already has a plan for catching Fleisher.
"Maybe if I stay in the same hotel as Fleisher tonight and beat him up a little bit," Thorpe joked.
Tom Kite also shot a 65 Friday as he and Thorpe tied the record for lowest second round score in a Senior Open, matching Gary Player's number in 1990.
Fleisher shot a 69 to sit alone at 133. Hubert Green had a 70 and fell two strokes behind.
"I can't make pars and beat those guys," Thorpe said.
Scores weren't quite as low as the opening round, when 22 players shot in the 60s. Rain forced a 95-minute delay Thursday and moistened the course, but didn't slow the greens much.
Hale Irwin shot par-71 and was tied with Kite for fourth at 137, four behind the leader.
Four players sat at 138, including Allen Doyle, who shot a 68 Friday. Jack Nicklaus shot a 75 after a solid first-round score of 67.
"It's the way I played most of the year," Nicklaus said. "Yesterday was an aberration. I don't have much positive to say."
Thorpe, however, was overflowing with enthusiasm.
After winning three championships in 23 years on the regular tour, Thorpe joined the seniors last year and placed among the Top 10 in nine of 36 events.
The closest he came to victory this year was tying for second in the Toshiba Senior Classic in March.
"I won't change anything," he said. "Last night I went down to an off-track-betting site, bet some races, ate some cheeseburgers and told some lies to the guys who were sitting there. I have to win to cut my losses from the betting."
Meanwhile, Arnold Palmer said his losses are getting too tough to handle. Palmer indicated he may have played his last Senior Open.
Palmer, a native of Latrobe, Pa., didn't fare well in his home state. He failed to make the cut for the second straight year after shooting rounds of 76 and 82
"I have a few commitments that I will keep tournament-wise and a couple exhibitions, but it is getting to the end of the line," said Palmer, who drew loud ovations on each hole.