Lewis, a 23-year-old who tied for fifth at the 2007 Kraft Nabisco Championship as an amateur, completed 54 holes at 9-under 210 for a one-shot lead over Paula Creamer. Creamer, a six-time winner on the LPGA Tour, had a 69 in the third round to move into second place at 211.
Helen Alfredsson and Inbee Park both shot 71 Saturday and are tied for third at 212.
Three-time U.S. Open champion Annika Sorenstam moved into a share of 13th at 217 after shooting 72 Saturday.
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