Hannah Green emerged from a rollercoaster round of one-over par 72 on Saturday with a one-shot lead over Lydia Ko in the LPGA Palos Verdes Championship.
Green started the day with a three-shot lead, but the Australian was in trouble early with three bogeys in her first six holes.
She rolled in an eagle putt at the seventh to stop the rot, but promptly dropped another shot at the eighth before a birdie at the ninth saw her make the turn one-over for the day.
With a string of players snapping at her heels, Green bogeyed the 12th.
A birdie at the 16th moved her to eight-under, tied for the lead with Ko, and when the New Zealander bogeyed the 17th, Green was left with a bit of breathing room heading into Sunday's final round.
Ko, who was among four players who started the day three strokes off Green's lead, got off to a shaky start herself with a double-bogey at the second and a bogey at the fourth.
But she charged back into contention with birdies at the fifth, seventh and ninth, and grabbed a share of the lead with back-to-back birdies at 15 and 16 before she was unable to get up-and-down from a bunker at the par-three 17th.
The world No 3 signed for a 70 and was alone in second on seven-under 206, two strokes clear of a group of nine players sharing third on 208.
That bunch included former world No 1 Park In-bee, who was tied for the lead at seven-under after an eagle at 16 but closed with two bogeys in a one-under 70.
She was joined on 208 by Americans Allisen Corpuz, Marina Alex, Andrea Lee, Lexi Thompson, Megan Khang and Annie Park, Scotland's Gemma Dryburgh and Australian Minjee Lee.
On a day when plenty of contenders struggled to keep mistakes to a minimum, Thompson powered up the leaderboard with an impressive five-under par 66 that featured six birdies and just one bogey.