Thorpe fired a 5-under 67 in the third round Saturday to take a two-shot lead at 13-under-par 203 -- ahead of a second-round leader Tom Kite, Jay Haas and Loren Roberts, who are at 11-under 205.
Seeking his 12th career Champions Tour win and first this season, Thorpe posted a bogey-free round at Sonoma Golf Club. He may need another one on Sunday.
'We all know Jay can take it low, and Tom Kite is a beautiful golfer,' said Thorpe, the 2003 Charles Schwab Cup Championship winner. 'I'm going to take some chances. I'm going to go out pin-hunting and force the action.'
Larger in scope than Thorpe's fight to win the season's final event is the showdown brewing between Haas and Roberts for the season-long Charles Schwab Cup and its $1 million bonus.
Roberts trails Haas by just 126 points. But points -- normally equal to 1/1000th of official prize money -- are tripled this week, leaving the Champions Tour in a similar position as last year when Tom Watson won with a birdie at the 72nd hole and passed Dana Quigley for the Schwab Cup.
Haas carded two eagles, five birdies and six bogeys in a round of 3-under 69. He went 10 holes without posting a par, beginning at the seventh, and ceded the top of the leaderboard to Thorpe when he made three straight bogeys from the 14th.
Roberts, meanwhile, scattered four birdies throughout a bogey-free round of 4-under 68.
'I'm a little surprised I'm only two back,' Roberts admitted. 'I thought Jay and Tom were off to the races. I guess it's going to be a shootout.'
Haas and Roberts will be split up for Sunday's final round, with Haas playing alongside Kite and Roberts joining Thorpe in the final pairing.
Kite, who holed out for three eagles over the first two rounds, shot a 2-under 70 on Saturday.
Bob Gilder and Gil Morgan both shot 4-under 68 and share fifth place with Andy Bean (69) at 10-under 206. The defending champion Watson is one shot further back at 207 following a 5-under 67.