SWEDEN'S Fredrik Jacobson took over at the top with a second-round 66 at the WGC-HSBC Champions in Shanghai.
Two behind American Keegan Bradley overnight, the 37-year-old birdied four of his first seven holes and, after picking up two more on the way home, signed for an 11-under-par halfway total of 133.
Jacobson, who had his first PGA Tour victory in America in June and was third in Malaysia last week, led Australian Adam Scott and South African Louis Oosthuizen by one.
Scott, winner of the last world championship in Akron, Ohio, in August, went one better than Jacobson with a 65, but last year's Open champion Oosthuizen had the round of the day -- a nine-under 63.
It looked set to be another great day for USPGA champion Bradley when he rolled in a 40-foot eagle putt on the second and a 10-footer for birdie two holes later.
But the 25-year-old had his first bogey of the tournament after he missed the ninth green, dropped another shot at the short 17th and needed a closing birdie to be two behind after a 70.
England's Paul Casey, who lost his PGA Tour card last month, was in joint fifth spot with American Bo Van Pelt after a 66, and world number two Lee Westwood had a 68 to be part of the group one further back.
Irishman Graeme McDowell sits on six under, while world number three Rory McIlroy hit seven birdies, but there were also four bogeys on his card and he has six strokes to make up.
The 22-year-old US Open three-putted the 12th from no great distance and, going for the green on the 288-yard 16th, he found the hazard on the right and bogeyed again.
Jacobson said: "It's been a great couple of days. I feel I've been striking the ball well and I've been setting up a lot of chances."
The world number 54 could go top of Europe's Ryder Cup standings with a win and said: "I haven't decided yet on the schedule for next year. It's going to depend a little bit on how I play. I'm starting to get into a lot of the tournaments where I can create points both on the European list and when it comes to world ranking points.
"But first thing's first and that's to keep getting better and keep playing well. I had a hard time with the sleep and the jet-lag last week. It was difficult to have a 12-hour change."