Lewis retains Evian Masters lead
The 27-year-old shot a course record 63 and led by two shots after the opening round and, with three birdies and an eagle at the long seventh on another day of perfect weather, she stayed ahead on 12-under-par.
However, she sits just one shot clear of South Korea's Lee Il Hee.
Helped by a great run of four birdies in a row from the 13th, Lee posted a 67 to take second place while Paula Creamer, who won here as a teenager back in 2005, and South Korean Park Inbee are joint third on nine under.
Creamer shot a 67 while Park had 64, the lowest score of the day.
Lewis, who broke through with a victory in last year's Kraft Nabisco Championship, has already won twice this year at the ShopRite and Mobile Bay LPGA Classics and has risen to No.3 in the world.
"To be honest, I struggled a little today," she admitted. "It is always tough backing up a really good score. In this weather, you have to make birdies. But it is hard not to push too much."
Lewis birdied the fourth and then made a raking putt for eagle at the seventh to reach the turn in 33.
She dropped her first shots of the tournament at the 12th and 14th but bounced back with a birdie at the long 15th and another at the eighth, where her chip for eagle lipped the hole.
Lee attributed her score to an improvement in her putting.
"I played really well and it feels good to be here," she said. "After the pressure of the US Women's Open, this tournament almost feels like a bonus."
On the day of the Olympic Opening Ceremony in London, Creamer revealed she had gone over Lake Geneva to Lausanne, seat of the IOC, for inspiration earlier in the week.
"Unfortunately, the Olympic Village was closed," she said. "But I went over there the year I won the tournament so I thought I would do it again.
"It is good to come to tournaments and soak up some of the culture."
Creamer has yet to make a bogey, and the 25-year-old had four birdies in her opening 68 and five in her second round.
At the 18th she was left with a tap-in after her third shot with a wedge nestled inches from the hole.
South Korea's Kim Hyo-Joo underlined her status as one of the world's best amateur players with rounds of 69 and 68 for a share of sixth place on seven-under-par.
Japan's Ai Miyazato, the defending champion who is chasing a third win in four years, had a 70 to go into the weekend on three under.
Karine Icher remains the best home hope, with the French veteran shooting 72 for two-under-par and a place around the top 40.
But the big shock was that Yani Tseng, the world No.1 from Taiwan, missed the cut that fell on two-over-par.
The 23-year-old, who has already won five majors, shot a 71 and missed by one on three-over-par.