Na Yeon Choi leads the CME Group Titleholders by one shot from Ai Miyazato with one round remaining in Florida.
South Korean Choi carded a three-under-par third round of 69 at the TwinEagles Golf Club on Saturday to reach 12-under overall and sit clear at the top of the leaderboard.
The 25-year-old, already a six-time winner on the LPGA Tour, made an inconsistent start to her third round, following her first birdie of the day at the par-five second with a bogey at three.
But she was a picture of consistency after that, sinking birdies at 10, 13 and 17, and making par on every other hole to lead the way going into Sunday's deciding round.
Japan's Miyazato is one stroke back in outright second following her one-under 71 on day three in Naples.
Choi's compatriot So Yeon Ryu also has designs on the title - she is just two shots back at 10 under courtesy of a four-under 68.
Two players are tied for fourth at nine under, with Frenchwoman Karine Icher and American Brittany Lincicome both posting two-under third rounds of 70 on Saturday.
China's Shanshan Feng and Swede Anna Nordqvist are a stroke further back, tied for sixth at eight under.
Karrie Webb is the best-placed Australian in the field, she is one of four players to hold a share of eighth spot at seven under.
Further back, Lindsey Wright is tied 27th at one under, while fellow Australian Katherine Hull holds a share of 30th, even par for the competition.
The defending champion, South Korean Hee Young Park, holds a share of 46th at three over after throughout her tournament defence.