Soo-Yun Kang remained alone in second place after a 2-under 70. She completed 54 holes at 12-under-par 204. Defending champion Annika Sorenstam struggled to an even-par 72 and is alone in third place at minus-9.
Brittany Lincicome (66) and Juli Inkster (69) share fourth place at 8-under-par 208.
Ochoa had a steady front nine going as she parred her first five holes. She moved into red figures with a 15-foot birdie putt at the par-4 sixth.
The Mexican made it two in a row as she birdied the par-5 seventh for the third straight round. Ochoa cruised around the turn with four consecutive pars on the Prospector Course at Superstition Mountain Golf and Country Club.
Ochoa, a two-time winner on the LPGA Tour, tripped to a bogey at the 12th to fall to minus-13 and a share of the lead with Kang. Things quickly turned at the next. Ochoa converted a 10-foot birdie putt, while Kang missed the green long and stumbled to a bogey for a key two-shot swing.
The 23-year-old Ochoa converted another birdie try at the 14th to move to 15 under. However, she faltered to a double bogey at the 16th after her drive came to rest in a bush forcing Ochoa to take an unplayable lie. She held onto to her lead with pars at the last two holes.
'I'm happy with my round today,' said Ochoa. 'I think I got away with things a couple times today. I was swinging a little bit fast and hit the ball a couple of times to the right and just made a bad swing on 16 and hit it way left.
'I think it was a tough day today. You can see the scores were higher. The wind changed direction and the course played very different.'
Kang flew out of the gates with birdies at one and two to join Ochoa in the lead at minus-12. However, the Korean bogeyed the third to fall one back after missing a short par putt.
The 29-year-old drained a 15-foot birdie putt at the sixth and made it two straight as she birdied the seventh. Kang bogeyed the 13th after Ochoa came back to her, but Kang responded with a birdie of her own on the 14th.
Kang slid three strokes behind Ochoa when she bogeyed the 15th after missing the green. Kang closed with three pars to remain at minus-12.
'At the beginning, I played very well, but at the ninth hole I missed a 2-foot birdie putt and after that I lost some confidence,' Kang said. 'I'm satisfied with where I am right now.'
Sorenstam opened with a birdie at the first, but the top player in the women's game stumbled to a double bogey at the par-4 third to fall back to 9 under.
The Swede, who won here in 2001 and 2004, got one stroke back when she birdied the ninth. Sorenstam parred the first seven holes of the back nine before dropping another stroke at the 17th. She came back with a birdie at the last for an even-par 72.
Rosie Jones carded an 8-under 64 to move into sixth place by herself at 7-under-par 209. Siew-Ai Lim and Liselotte Neumann were one stroke further back at minus-6. Candie Kung was joined in a tie for ninth at 5-under-par 211 by Grace and Gloria Park.