Lewis birdied five of her last nine holes on her way to a 5-under 67 and an overall 9-under 135 at the Robert Trent Jones Golf Trail's Magnolia Grove complex, an astonishing bounce back after a terrible showing in last week's event.
"It was really one of those weeks," Lewis said of her missing the cut a week ago in Hawaii. "I had a lot of stuff going on. Mentally I was kind of not there. I'm a lot more relaxed this week. I just kind of chalked one up to a bad couple of days, and I'm just kind of moving on.
Karin Sjodin equalled the tournament course record with a 64 to sit a stroke back at the halfway stage, tied in second alongside Lindsey Wright, So Yeon Ryu and rookie Sydnee Michaels.
"Playing in the second-to-last group, it was a little bit difficult to read putts and make putts," Australian Wright said.
"I think I hit it just as good on this (final) nine. It's disappointing not to birdie anything, but I'm in a great spot coming into the weekend.
Two strokes back was a group of six players, including Kraft Nabisco winner Sun Young Yoo.