Rory McIlroy shot a stunning 11-under-par round of 61 to storm to the top of the leaderboard at the Wells Fargo Championship in North Carolina.
The world number one started the weekend three shots off top spot but he produced a record-breaking display in his third round to overhaul all his rivals.
McIlroy parred his first two holes before going on to pick up 11 birdies - including nine in 10 holes at one stage - in a second successive blemish-free round to move to 18-under par for the tournament.
It was the Northern Irishman's lowest round on the PGA Tour, beating the 62 he made here in 2010 - the previous course record at Quail Hollow.
McIlroy had looked on target to shoot a sub-60 round - only six players have ever scored 59 in a PGA Tour event - but he had to settle for pars on the final two holes
Despite that, McIlroy's remarkable display left him with a four-shot lead heading into the final day, with Webb Simpson his nearest challenger after the local hope carded a 68.
American Robert Streb, who led after the first round and was joint-top with Simpson at the halfway stage, is a further three shots back in third place.
"Even though I've got a lead there's no reason why I shouldn't go out there and be aggressive and try make as many birdies as I can" - Rory McIlroy
McIlroy told Sky Sports of his round: "It was incredible, it was nice just to get on a run like that.
"I felt like every shot I looked at, I was comfortable over it and I really putted well today, that was the thing that pleased me most.
"I rolled the ball really, really nicely, and I don't think I've rolled it like that in quite a while, so it was nice to see a lot of putts drop.
"And to break my own course record here is pretty nice."
The four-time major winner, who felt he played too conservatively in the second round and felt he was rewarded for going for more pins today, is now clear favourite to become the first two-time winner of the event.
He is also on course to smash the existing overall tournament final record of 16 under, set by Anthony Kim in 2008.
And McIlroy insists he has no intention of letting up on the final day.
He added of his hopes for Sunday: "More of the same would be nice obviously! But just keep it going.
"Even though I've got a lead there's no reason why I shouldn't go out there and be aggressive and try make as many birdies as I can.
"I'm obviously playing well and I feel like this is a course where I can shoot another low score on."
In joint fourth place are Brendan Steele (68) and Patrick Rodgers (70) on 10 under, while Phil Mickelson, who shot a 66 on Friday, is back in a group on eight under after a damaging treble-bogey seven on the 18th left him with a 71.