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David Goldman, Associated Press
One supporter waves an American flag, and other waves a campaign banner, during a campaign rally for Republican presidential candidate, former Massachusetts Gov. Mitt Romney, Friday, Jan. 20, 2012, in North Charleston, S.C.

GREENVILLE, S.C. — Mitt Romney is heading into primary day conceding that he'll win some and lose some.

Romney on Friday acknowledged the contest here is "neck-and-neck" and said he expects to lose "some primaries" to rival Newt Gingrich, the former House speaker.

As voters head to the polls Saturday, the nature of the race has changed. The past week has been an abrupt reversal of fortune for the former Massachusetts governor, who landed here last Wednesday after a big victory in New Hampshire and what was then a narrow win in Iowa.

But this week the Iowa GOP reversed his win there after problems with the vote count, and he's been dogged by questions about releasing his tax returns. A loss Saturday would leave Romney with just one early state win.