Phil Mickelson, who at 50 is bidding to become the oldest player to win a major, was clinging to a two-shot lead over Brooks Koepka and Louis Oosthuizen midway through his final round at the PGA Championship on Sunday. Mickelson, who began the day with a one-shot lead over playing competitor Koepka, withstood a roller-coaster start to reach the turn at the Ocean Course at even-par 36 and seven under on the week. The five-times major champion surrendered his overnight lead on the first hole where he three-putted for bogey from 57 feet while Koepka made birdie to pull one shot clear. But Mickelson responded immediately with a birdie at the second and, compounded by four-times major champion Koepka"s double-bogey, was suddenly in front by two shots. Mickelson went on to bogey the par-four third, where his putt from 29 feet stopped just beside the cup, and Koepka squandered a chance to move into a share of the lead when he missed a three-foot birdie putt. Mickelson then whipped the limited number of spectators into a frenzy when he holed out a bunker shot for birdie from 50 feet at the par-three fifth to restore his two-shot cushion. Koepka moved into a share of the lead at the par-four sixth when he followed Mickelson"s bogey with a birdie after stuffing his approach shot to three feet. Another two-shot swing came at the par-five seventh to put Mickelson, who firmly drained a nine-foot birdie putt, back in front by a pair after Koepka"s bogey. Oosthuizen, whose sole career major triumph came at the 2010 British Open, had a much steadier outward nine as he mixed one bogey with a birdie to stay in contention.