Minjee Lee is tied second but has a mountain to climb to catch tour great Inbee Park if she's to win in her first start for the year at the LPGA Kia Classic.
Chasing a sixth career victory, 24-year-old Australian Lee shot a four-under 68 in the third round at Aviara Golf Club in Carlsbad, California - which included an eagle on the driveable par-4 9th.
She climbed from sixth spot to join South Korean Mi Jung Hir (67) and England's Mel Reid (71) at seven under.
However, they are five shots behind the formidable Park, who got to 12 under with a 69 as the world's best players fine tune for the year's first major, the ANA Inspiration next week in Rancho Mirage.
Like Lee, world No.4 Park is making her first LPGA start of the season but the 32-year-old South Korean star, who boasts 20 tour victories, seven of them majors, is showing few signs of off-season rust.
Starting the day with a one-shot advantage, Park played steady golf with four birdies and a bogey as she took advantage of the course being set up some 300 yards shorter for the third round.
"It was actually a big surprise," Park, runner-up in this event in 2010, 2016 and 2019, said.
"I didn't know the LPGA was going to move four tees up in one day. I never seen this kind of set-up before. So they tried something new.
"I mean, it took a long time on the golf course today waiting to go for the greens. But it was fun at the same time.".
Reid played alongside Park and admitted it would be a big task to overhaul her on Sunday.
"She's got a five-shot lead, so I'm going to have to do something special to get it done tomorrow," Reid said.
World No.1 Jin Young Ko (68), American star Lexi Thompson (66) and Sweden's Madelene Sagstrom (64) are all in the picture as well, tied fifth at six under.
Sagstrom had the round of the day, overcoming an opening double bogey for her 64.
The Swede followed the double bogey with birdies on seven of the next eight holes. She had four birdies and a bogey on the back nine.
American Marina Alex had a wild finish to her round of 71, closing bogey-eagle-bogey-eagle which included holing out from the fairway on the par-4 18th.