Fredrik Jacobson was in pole position in the World Golf Championships-HSBC Champions in Shanghai as the leading contenders approached the midway point of their final rounds.
The Swede held a two shot advantage over England's Paul Casey, with Northern Ireland's Rory McIlroy a further shot back.
Jacobson bogeyed the first hole for the second time this week - but responded with birdies on the second and sixth to move to 17 under.
Casey appeared to have slipped out of contention with a bogey on the second, before birdies on four of the next five holes reignited his challenge.
McIlroy moved into contention with birdies on the first two holes - before his progress was halted by a run of pars from holes three to seven.
Bo Van Pelt of the United States joined McIlroy on 14th under with an eagle on the eighth, while South Africa's Louis Oosthuizen was alongside them.
Oosthuizen moved back into contention with birdies on the seventh and eighth - after dropping two shots in the first four holes.
However, Lee Westwood's challenge seemed to have ended as a double bogey on the seventh saw the Englishman slip back to ten under, seven shots off the pace.
