Stenson had four birdies in the last five holes, capping a 5-under-par 67 with an 18th-hole birdie. That left him just ahead of Dubuisson, who turned in an 8-under 64. Stenson, the top qualifier for the World Tour Championship, is at 17-under 199 after 54 holes; Dubuisson is 16-under.
Miguel Angel Jimenez is alone in fifth place after his 6-under 66 Saturday put him at 12-under for the tournament. Lee Westwood (65 Saturday) and Justin Rose (68) are tied for sixth another stroke back.
Dubuisson, who hadn't won a professional tournament before last week, opened play Saturday with a bogey but then ran off four straight birdies. Birdies at Nos. 7 and 8 allowed him to make the turn at 5-under.
But Dubuisson had a double-bogey 6 at the 10th hole. He came back with a birdie at 11 and pulled into a tie with the lead with three-straight birdies at 13-15 before the late charge by Stenson. Dubuisson kept the pressure on with a birdie at 18.
Stenson had a more sedate start to his round with two birdies and seven pars in the opening nine. He bogeyed the 10th hole -- just his second bogey of the week -- but stemmed the challenge from Dubuisson with birdies over Nos. 14-16. He tapped in a 1-foot putt for birdie at 18 and the outright lead.