Shanghai: Fredrik Jacobson capitalised on poor putting by overnight HSBC Champions leader Keegan Bradley on Friday to storm to the top of the leaderboard at 11-under-par.
Jacobson dazzled with a 6-under-par 66 second round score to add to his opening account of 67 and take control at the halfway stage in the China showcase.
"It's been a great couple of days and I've been striking the ball well and setting up a lot of chances," said Jacobson.
Major winner Bradley, the current PGA champion, dropped to fourth on 135 despite starting strongly by holing a 40 foot eagle putt on the 2nd hole of the Sheshan International Golf Club.
However, Bradley missed a number of putts on the back nine and two bogeys on his card meant he entered the clubhouse with a score of 70, nine-under-par overall.
"I didn't play well. I could have been 5 or six under on the front nine," Bradley said. He added though that he was "only two back".
Breathing down Jacobson's neck in tied second on 10-under are South African 2010 Open Champion Louis Oosthuizen and Australian Adam Scott.
Flawless Oosthuizen raced from his first round one-over to seven-under by the 15th hole and carded nine birdies overall in a blistering second round score of 63.
"I don't think I missed a green today. I made 20-foot putts go in for a change. It was good, solid day," the 29-year-old said.
Akron World Champion winner Scott began to feel his way on the softening course which endured more overnight rain, carding nine birdies and two bogeys to score one better than Jacobson.
Malaysia PGA Tour winner American Bo Van Pelt kept in touch with the leaders with a three-under 69 and is in joint fifth with England's Paul Casey on an eight-under-par overall score of 136.
Germany's 2010 PGA champion Martin Kaymer and Australian Aaron Baddeley both shot 4-under-par 68s and moved into joint seventh place alongside world number two Lee Westwood on seven-under.
Englishman Westwood bogeyed the 10th hole and missed a putt on the 16th by a whisker but maintained his presence with his five birdies.
He described his first two rounds as a "work in progress".
"I could have bogeyed the last six holes but I didn't. 69 is a pretty good score. I'm only four behind and well within touching distance. There's a lower score out there," said Westwood.
World number three Rory McIlroy carded a disappointing 69 despite the close support of his girlfriend, world number one women's tennis ace Caroline Wozniacki.
The US Open Champion's four bogeys countered his seven birdies to leave him tied 17th on five-under overall.
"Every time I made a birdie, I made bogey and I was just always trying to play catch up. It's one of those things and I'll have try and make them up over the weekend," the 22-year-old said.
It was the first time that the Dane has offered her support to McIlroy on the links - a reciprocation of his recent loyal tennis court side presence.
Asked if her companionship added extra pressure, he replied: "No, not at all. It's nice to have her support out there."
The couple regularly swapped romantic glances with each other, with Wozniacki offering the Northern Irish star a sympathetic smile after each of his bogeys.