Lewis, who is chasing her third LPGA Tour title of the year, had a 1-over 73 to finish the day at 11 under. The overnight leader had two bogeys and a double bogey on the back nine before a birdie on the 18th.
"I feel like I'm still in the tournament, and just got to make some putts tomorrow," said Lewis, who equaled the course record in her opening round. "I shot 63 the first day, so I know I can play good out here. I'm not too worried about it."
Park, who was three shots behind Lewis in third place overnight, had four birdies and two bogeys for a 70.
Karrie Webb (67), Natalie Gulbis (68) and 17-year-old amateur Hyo Joo Kim (69) of South Korea were one shot behind the leaders.
"Amazingly, it was my best round of the week, but probably not my best ball-striking day," said Webb, the 2006 Evian winner, after making six birdies. "I made a couple of nice long ones."
Gulbis, the 2007 champion, had an eagle on the ninth hole.
"The change in my round (was) that I eagled nine," Gulbis said. "So that definitely turned my round in the right direction."
Cristie Kerr had a 67 to finish two shots back.
A light rain started in the morning, followed by a heavy downpour at lunchtime. But Kerr played through the worst of the weather.
"I played great," Kerr said. "Really just started raining a lot and became hard to make your normal swing."
Lewis, after making a birdie on 11, teed off into the rough on the next hole and finished with a bogey. She had another bogey on the 14th and a double bogey on the next hole.
"I think I was trying to be a little too cute with my third shot and just really hit a bad shot," Lewis said of the double bogey. "The first chip actually had a pretty good lie, but just the grass being wet from the rain obviously affected that shot."
That made the birdie on the 18th sweeter.
"I knew I needed to make birdie to get in the last group," Lewis said. "It's also nice just to see a putt go in."
Cheyenne Woods, Tiger Woods's niece, was 6 under after a 70.
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