First-round leader Angela Stanford still held the lead early Friday afternoon at the LPGA Safeway International, but Lorena Ochoa, Jee Young Lee and Annika Sorenstam made charges with rounds of 67.
Stanford followed her best career round of 62 with a 69 Friday to go 13-under.
Ochoa, the No.1 ranked player in the world, was one shot back after shooting a 5-under second round at the Supersition Mountain Golf and Country Club.
Lee is at 10-under after two rounds. Sorenstam is at 8-under, five behind Stanford.
Christina Kim birdied two of her final three holes to finish with a 4-under 68, leaving her six shots off the lead.
Michelle Redman shot a 4-under 68 to tie Sorenstam for fourth place at 8-under.