Welshman Jamie Donaldson, four clear of the field overnight after a stunning course-record 62, soon had company at the top of the leaderboard at the BMW Masters in Shanghai today.
While he followed five pars with a bogey at the short sixth, failing to get up and down from a bunker, back-to-form Swede Robert Karlsson made a spectacular charge through the star-studded field in his second round.
Only 39th after an opening 71, the former Ryder Cup player had eight birdies in his first 11 holes and with three holes to play remained nine under par.
Ireland's Shane Lowry, winner of the Portugal Masters two weeks ago, was another to make a big move. He went round in 64 and on eight under was up from 48th to joint third with Swede Peter Hanson.
World number one Rory McIlroy remained well in touch, picking up shots on the second and third and after seven holes stood joint fifth with his fellow Northern Irishman Michael Hoey.
Ryder Cup captain Jose Maria Olazabal, able to focus on his own game again after the drama of Chicago a month ago, mixed two birdies with two bogeys over the initial six-hole stretch and with that slipped back from joint fourth into a tie for 13th with, among others, his team members Luke Donald, Justin Rose and Graeme McDowell.
Lee Westwood and Ian Poulter were one further behind.
Donaldson played a far better bunker shot on the long seventh and grabbed his first birdie - yesterday he had 10 - but he went from more sand into water down the next and followed one bogey there with another on the next.
From four clear he was down to joint fourth and two behind new leader Hanson, who had five birdies in six holes from the third.
Karlsson parred the final seven holes to match Lowry's 64 and was tied for second with McIlroy, who completed a front nine 32 with back-to-back birdies and remained favourite for the title.
Rose, meanwhile, moved alongside Lowry and Donaldson with a spectacular six birdies in seven holes around the turn.