Without her best stuff, Yani Tseng carded a four-under 68 on Friday to grab a two-stroke lead after the second round of the Kia Classic.
Tseng, who was one of three leaders after the first round, completed 36 holes at nine-under-par 135.
Se Ri Pak fired a six-under 66 to jump into second place at minus-seven.
Caroline Hedwall, who shared the first-round lead with Tseng and Ji Young Oh, managed an even-par 72 to slide into a share of third at five-under-par 139.
Hedwall was joined there by Alison Walshe (66), Jodi Ewart (69) and Jiyai Shin (71) on the Legends Course at La Costa Resort & Spa. Brittany Lincicome (73) and Jennifer Johnson (73) are tied for seventh at minus-three.
Oh struggled to a four-over 76 and fell into a share of 14th place at one- under 143.
Tseng parred the first two holes before catching fire. She birdied the par- five third and followed with birdies on four and five to move into the lead at minus-eight.
It looked as though Tseng would run away from there, but trouble loomed. She stumbled to bogeys on the seventh and eighth to fall one behind.
Tseng dumped her approach shot into a greenside bunker at the par-four 10th, but she holed the sand shot for birdie to move back into a share of the lead.
After a pair of pars, Tseng again chipped in for birdie at the 13th to go one ahead. She parred the next four holes before rolling in a long birdie putt at the par-four 18th.
"Today, I made some little stupid mistakes on the front nine," Tseng admitted. "I just stayed really patient, and I was very happy that I finished with four- under today.
"I had two good days, and hopefully the next days I can keep the rhythm and be patient. I'm looking forward to the next two days."
Pak had a remarkable front nine with six birdies. She opened with a birdie at the first, then carded three in a row from the third. Pak birdied the seventh and came right back with a birdie on No. 8 to move to seven-under.
The 34-year-old Pak, who is already in the World Golf Hall of Fame, tripped to a bogey on the ninth. Around the turn, she birdied the 13th, but gave that shot right back at 14. Pak birdied the par-five 17th to end alone in second.
"Overall, I'm making a lot of putts. But at the same time, I had a lot of great shots too," Pak said.
NOTES: Defending champion Sandra Gal stumbled to a four-over 76 to fall into a share of 50th at plus-four...Lincicome had a hole-in-one on the par-three sixth...The cut line fell at five-over-par 149 with 75 players moving on to the final two rounds...Christina Kim, Ryann O'Toole, Women's Australian Open winner Jessica Korda, Maria Hjorth and Laura Davies were among those that missed the cut.