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In the three years since Stacy Lewis lost a third-round lead at the U.S. Women's Open in her first pro tournament, she traveled the globe, opened her mind and thoroughly revamped her game.

A few bad iron shots and a little desert heat just aren't such challenges any more.

Lewis persevered through more triple-digit temperatures to shoot a 3-under 69 at the Kraft Nabisco Championship on Friday, opening a three-stroke lead over Yani Tseng, Brittany Lincicome and Jane Park.

Michelle Wie shot a 67, matching the day's best round and closing within six shots in contention for her first major title. Tseng, the defending champion and the world's top-ranked player, shot a 68, while first-round co-leader Lincicome mustered a 72 to stay one stroke ahead of Morgan Pressel and Amy Yang.

The leaders all managed to thrive on dry, speedy greens during a second windless day at Mission Hills, with the temperature topping 100 degrees by midday.

But Lewis pulled ahead at 9-under par after several big putts during the second round, smoothly reaching the halfway point of the LPGA Tour's first major in strong position to chase her first victory during what's expected to be a cooler weekend.

"My round was all over the place," said Lewis, who shared the first-round lead. "But I made some really good up-and-downs and stayed really patient on the back nine, and I was fortunate to get away with a couple of pars that I probably shouldn't have."

Big things were expected from Lewis after she burst onto the tour with a third-place finish behind Inbee Park at Interlachen in 2008, nearly becoming the first player to win a major in her professional debut.

Although she's now a solid pro, finishing 21st on last season's money list, she hasn't won. She's still enduring the maturation of any player coming out of college — finding a swing guru, figuring out the hectic travel schedule and mentally managing through weeks away from home, sometimes on the opposite side of the globe from her home in Texas.

"I just feel like I have a really good group of people around me now," Lewis said.

That group sometimes includes Lincicome, her road roommate and good friend. It also includes Betsy King, who accompanied Lewis on a trip to Africa with Lewis' mother.

Her experience in Rwanda, meeting families in a daily struggle for water and survival, affected her just as much as her ongoing charity work with dozens of young people with scoliosis, the same spinal affliction she overcame.

"I saw things (in Rwanda) I never thought I'd see in my life," Lewis said. "It was such a shock to me that people live the way that they do, but they are so happy and so grateful. It just makes me grateful for everything that I have, and it gave me a renewed purpose of what I'm doing out here. The better I play golf, the more I can help other people, the more I can inspire other people."

Lewis had to be resourceful from the opening holes Friday. She made tough putts on three straight holes before putting her tee shot on the nine behind a tree. She saved herself with a 200-yard hybrid shot and an up-and-down par before finishing strong with a bogey-free back nine.

Lewis and Wie memorably went to the same LPGA Q-school in December 2008. While Wie's presence got all the headlines, Lewis had the five-round event's best score.

Wie was 2 over in Thursday's first round, but she rallied impressively Friday morning after a horrible start.

Her first tee shot flew into the gallery and beaned a little girl, who needed attention from paramedics. Wie couldn't stick around to see how she was doing.

"I never felt so horrible about a shot ever," said Wie, who has drilled a few spectators in her day with a sometimes-erratic approach from the tee. "I felt so horrible about hitting that poor little girl. ... I thought I had hit a sprinkler or a tree or something. The little girl was the last thing on my mind, but hopefully she's OK."

Park played her way into the Kraft Nabisco field with a top-30 finish at last week's Kia Classic. The Los Angeles-area native, who missed the 2009 season with a back injury, excelled on the dry, fast greens of Mission Hills, which she first played when she was 16.

"The first time I played here, the golf course is just so visually intimidating," Park said. "Now, it still looks intimidating, but I'm not really afraid of the golf course, which is what was running through my mind as a kid."