Mitt Romney has a big lead in the polls and his rivals are searching for ways to slow his momentum.
He said he is aware of the negative advertising about his stand on social issues.
Former House Speaker Newt Gingrich is describing Romney as a Massachussetts moderate.
Texas Governor Rick Perry is describing Romney's work as a "vulture capitalist," instead of a venture capitalist.
The South Carolina primary will be held Jan 21.
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