Mickelson was one of four golfers at 14-under 202 through 54 holes and can claim his first European Tour victory Sunday if he can catch Stenson , who also carded a 66 Saturday to go 16-under.
Mickelson collected a flock of six birdies, including four of the five holes around the turn and the 18th hole. He hit 11 of 14 fairways and needed 26 putts compared to 31 in each of his first two rounds.
Branden Grace and John Parry also scored 66 Saturday to stake a claim to second place along with JB Hansen, who cooled off with a 69 after a 65 on Friday.
Stenson bogeyed the ninth hole but he scored birdie on four holes on the back nine to finish 6-under for the day after scoring an 8-under 64 on Friday.