Phil Mickelson overcame a back-nine wobble to cling onto a one-shot lead after an enthralling third round at the PGA Championship.
The 50-year-old, looking to become the oldest winner in major history, had raced into a five-stroke lead after birdieing five of his opening ten holes at Kiawah Island’s Ocean Course, only to drop three shots in the space of two holes to bring the chasing pack into play.
A five-par finish gave Mickelson a two-under 70 and gave him a narrow advantage over four-time major champion Brooks Koepka, who held a share of the advantage until bogeying the final hole of his third-round 70, with overnight co-leader Louis Oosthuizen a further stroke back in third on five under.
Mickelson moved ahead when Oosthuizen made a three-putt bogey at the first and doubled his advantage when an incredible long iron set up a two-putt birdie from 15 feet at the par-five next.
The five-time major champion splashed out of the sand to tap-in range and picked up a shot at the third, before following a 15-foot birdie at the sixth with a two-putt birdie at the par-five seventh to find himself four ahead.
Koepka, playing the group ahead, had cancelled out a 12-foot birdie at the fifth with a dropped shot at the next and then gave back a close-range birdie at the seventh with a bogey at the ninth to find himself five behind at the turn.
Mickelson had produced a remarkable up and down to save par at the ninth and went further clear when he rolled in a seven-foot birdie at the tenth, only to begin his decline when he failed to convert from a similar distance to take advantage of the par-five next.
Oosthuizen holed an eight-foot birdie at the 11th to get within four of Mickelson, as Koepka followed a birdie at the tenth by nailing a 20-footer at the 12th to join the South African in a share of second.
Mickelson was forced to lay up from the sand at the 12th on his way to a first bogey of the day, as Oosthuizen made a ten-foot birdie for a two-shot swing, only for both players to find water off the tee at the par-four next.
Oosthuizen was able to scramble a bogey and close the gap to one when his playing partner, having to reload from the 13th tee, carded a double-bogey, with Mickelson then wasting an eight-foot birdie attempt after a glorious tee-shot into the par-three next.
Koepka had squandered a 10-foot birdie try at the 14th but jumped into a share of the lead with a two-putt gain after a scintillating approach into the 16th, where Mickelson recovered from a wayward drive to avoid dropping another shot and stay at seven under.
Oosthuizen missed a five-foot birdie attempt at the 16th and putt from a similar distance to save par at the par-three next, dropping him two behind, while a par for Mickelson was enough for him to edge back ahead when Koepka three-putted from the just off the back of the green to bogey his final hole.
Mickelson delivered a short-game masterclass on the final green to pitch from the bottom of the bank to six feet and save par, retaining his narrow advantage, with Oosthuizen also finishing with a par to complete a level-par 72 and sit two off the pace.
Kevin Streelman heads into the final round in fourth spot and on four under, despite closing his two-under 70 with a bogey, while Christiaan Bezuidenhout recovered from bogeying his opening two holes to sign for a level-par 72 and sit in tied-fifth alongside compatriot Branden Grace.
A final-hole birdie lifted US Open champion Bryson DeChambeau into a share of seventh with Gary Woodland and Joaquin Niemann, with Paul Casey one of three players in tied-10th despite a one-over 73.
Jordan Spieth, chasing the career Grand Slam, remains seven behind despite a four-under 68, while Rory McIlroy saw his slim victory hopes ended when he dropped into the group on five over after a third-round 74.