Carol Platt Liebau
It's a big night for Mitt Romney -- almost, I would say, either the beginning of the end or the end of the beginning.

Lots of Republicans will be watching tonight's debate carefully.  If Romney cannot fend off a challenge from a manifestly flawed candidate like Gingrich, then he's toast when he comes up against the President's slick political machine.

Romney doesn't have to out-Gingrich Gingrich tonight.  But he does have to show resilience, the ability to learn (McCain's 2008 campaign manager once described him as a "learning organism" -- we'll see if he's right), the heart to come out fighting, and the capacity to make a case for himself in a way that allows him to connect, at least to some degree.

His success or failure may determine whether South Carolina is a blip or the beginning of a long slide that spells danger for the GOP's chances next November.

Carol Platt Liebau

Carol Platt Liebau is an attorney, political commentator and guest radio talk show host based near New York. Learn more about her new book, "Prude: How the Sex-Obsessed Culture Hurts Young Women (and America, Too!)" here.