On a Saturday when many players near par 73 to claim the lead after three rounds of the Women's Australian Open.
The American Korda sits at four-under-par 215, one shot in front of Nikki Campbell, Hee Kyung Seo and So Yeon Ryu.
The shuffling of the leaderboard came after another tough round at the Royal Melbourne Golf Club.
Ryu, the reigning U.S. Women's Open champion, was the second-round leader but stumbled to a three-over 76 on Saturday. She reached minus-eight early in her round and looked like she might take control of the tournament, but went on to post six bogeys.
Seo was right below Ryu after the second round, but carded a 75 on Saturday.
"It's one of the hardest courses I have ever played," said Seo. "It's probably in the top-five or the top-three, and sometimes the breeze is quite crazy. Also, the green is firm and fast, plus the undulations. Most of the players struggled at times."
Campbell was one of a few players to take advantage of the second-round leaders' struggles, firing a 70 to gain a share of second place.
"The wind was a lot stronger than the first two days," Campbell said. "You had to trust your shots a lot more and stay patient."
Two-time defending champion Yani Tseng (71), Katie Futcher (71) and Lorie Kane (72) are tied for fifth at two-under-par 217.
Ryu and Seo were threatening to pull away from the field early in their rounds.
Ryu birdied the par-five second and followed that with another birdie at the par-three third. Meanwhile, Seo birdied the third, after which Ryu was at eight-under and Seo sat at six-under.
But Ryu's round started to unravel when she gave both shots back with bogeys at the fifth and sixth. She birdied the eighth, but again followed that up with a bogey to make the turn at six-under.
Seo also birdied the eighth, but posted a bogey at the holes immediately before and after and made the turn at five-under.
They began the back nine with their scores back where they were after the second round, but both continued to struggle.
Ryu didn't have a single birdie during her final nine holes, instead recording bogeys at the 11th and 14th. She still had a share of the lead heading to the last, but bogeyed that was as well to drop into second.
Seo double-bogeyed the par-four 14th and bogeyed the 16th to fall two shots behind Korda, but ended the round on a positive note. A birdie at No. 18 lifted her into second.
Like Ryu and Seo, Korda had an up-and-down round. She bogeyed the fifth, but responded with birdies at Nos. 7, 9 and 10 to reach six-under. That would have left Korda as the decisive leader had she stayed at that score, but she dropped shots at the 13th and 17th.
Korda is the daughter of Petr Korda, a former professional tennis player who won the 1998 Australian Open.
"My dad was world No. 2," Korda said. "I told him I want to beat that. It would be a great accomplishment, an awesome thing."
Julieta Granada and Melissa Reid were tied for third with Korda after the second round, but both endured above-par rounds on Saturday. Granada shot a 76 to fall into a tie for eighth at one-under with Brittany Lincicome (73). Reid posted a 77 and sits at even-par overall, tied for 10th with first-round co- leader Stacy Lewis (77).
NOTES: Only nine players sit below par...German Sandra Gal began the third round in contention at one-under, but shot a 10-over 83 on Saturday to tumble into a tie for 53rd...Amateur Lydia Ko, 14, fired a 72 and sits in a tie for 18th at three-over 222. Ko is the youngest winner of a professional golf tournament, having claimed the title at the NSW Open in January.