Stacy Lewis shot a superb third round 65 on Saturday to hold a three-shot lead at the Cambia Portland Classic.
Lewis, from Houston, has pledged to give all her earnings this week toward the Hurricane Harvey relief effort back home.
Should the 11-time LPGA Tour champion win for the first time since June 2014, she will be handing over $195,000.
Tied for the lead overnight alongside two-time defending champion Brooke Henderson and In-Gee Chun, Lewis fired eight birdies as she shot a seven under round to finish on 17-under par.
She made one bogey all day, at the 16th to go with eight birdies.
A good round on Sunday and she could beat the tournament record low score of 21-under par, set by Henderson in 2015.
— Portland Classic (@PortlandClassic) September 3, 2017
Thailand’s Moriya Jutanugarn, younger sister of former world number one Ariya, was three shots behind Lewis after shooting a 66. Chun (69) was one shot further back.
Jutanugarn made six birdies on her first 10 holes as she searches for her first LPGA Tour title.
Henderson enjoyed a disappointing afternoon, shooting a two-over 74 to drop back into a tie for 13th at eight under par.
Lewis has two previous runners up finishes in Portland including last year when she ended up four shots behind Henderson.