Cristie Kerr and Jee Young Lee both posted rounds of 2-under 70 and are knotted in second place at 7-under-par 137. Canadian Lorie Kane also carded a 70 on Friday and is alone in fourth place at minus-6.
She parred the 12th, but found trouble with her approach at the 13th. Stanford's 6-iron shot ran through the green and her chip flew 8 feet past the hole. She narrowly missed the par putt and fell back to 9 under par for the championship.
Stanford drained a crucial par save at the 18th, then parred her next three holes on the front side. At the par-5 fourth, Stanford laid up short of the putting surface with her second, then wedged her third to 8 feet. She holed the birdie putt to move to minus-10.
From there, Stanford continued to make pars. She finished with five in a row to close her round, but owns a three-shot margin in her bid for LPGA Tour victory No. 2.
'I was more frustrated today than I was yesterday obviously,' said Stanford, who lost a playoff at the 2003 U.S. Women's Open. 'I think a lot of it has to do with playing in the morning and the afternoon. The greens felt like they were getting firmer and firmer.'
Stanford has owned the second-round lead twice on tour with mixed results. She held on for her lone LPGA Tour victory at the 2003 ShopRite LPGA Classic, but tied for second earlier this year at the Franklin American Mortgage Championship.
This week, she's armed with a three-shot advantage heading into the weekend, but the 28-year-old knows that no lead is safe.
'It's never enough, never enough,' acknowledged Stanford. 'You can give me 10 shots right now and it wouldn't be enough. These ladies, they're so good, and on any given day, they can do what I did yesterday.'
Kerr was 1 over through her first 10 holes on Friday, but turned it on down the stretch. She rolled in a 6-foot birdie putt, then chipped in for birdie at the 12th.
Kerr, who overtook Stanford at the Franklin American Mortgage Championship, hit a pitching-wedge to 5 feet to set up birdie at the 15th. She had makable looks at 16 and 18, but missed, leaving her three behind.
'Regardless of who is at the top of the leaderboard, I have to go out and play the course as best I can,' said Kerr, who tied for second last week at the Women's British Open. 'I think the course is going to do nothing but get harder, with the hole locations and the firmness of the greens. So I've really just got to go out and play my game.'
Lee, who has not missed a cut since the second event of the season at the Fields Open in Hawaii, mixed four birdies and two bogeys in her round. Three of her birdies came in her last five holes.
Vicki Goetze-Ackerman shot a 1-over 73 and Pat Hurst, who lost to Annika Sorenstam in a playoff at this year's U.S. Women's Open, posted a 71 to share fifth place at minus-4.
Sophie Gustafson, who shared second with Kerr last week, fired a 3-under 69 and is tied for seventh place with defending champion Meena Lee, who shot a 1-over 73 on Friday. The pair is knotted at 3-under-par 141.
The 36-hole cut fell at 5-over-par 149 with 83 players making it to the weekend.