Campbell had the best round of the day with her 70. She had five birdies and two bogeys.
“Every player would want to win her national championship in any sport,” said Campbell, a regular on the Japan LPGA. “Being in a position where I have a chance is more than I could have asked for.”
Only nine players were under par after three rounds, with long-hitting American Brittany Lincicome and Paraguay’s Julieta Granada three strokes back at 1 under. Lincicome had a 73, and Granada shot a 76.
A day after shooting a tournament-best 66, Seo had three birdies, three bogeys and double bogey in her 75.
“It’s one of the hardest courses I have ever played,” said Seo, a playoff loser to Ryu last year in the U.S. Women’s Open. “It’s probably in the top five or the top three and sometimes the breeze is quite crazy. Also the greens are firm and fast, plus the undulations. Most of the players struggled at times, but that’s golf.”
American Stacy Lewis, 4 under after opening rounds of 69 and 73, was even par after a 77.
Fourteen-year-old New Zealand amateur Lydia Ko was 3 over after a 72, one of only nine sub-par rounds Saturday. She won the New South Wales Open two weeks ago to become the youngest winner of a sanctioned professional tour event.
Australian star Karrie Webb, a four-time winner in the event, was 6 over after her third straight 75.
Second-ranked Suzann Pettersen also was 6 over after a 74. The Norwegian star opened with an 80 — the second-highest score of her LPGA Tour career — and had a 71 on Friday to make the cut.
The LPGA Tour is sanctioning the national championship for the first time, teaming with Australian Ladies Professional Golf and the Ladies European Tour.