While Newt Gingrich's win in SC was impressive (he won by even more than I thought-see last post) he's absolutely toxic in a general election. While Barack Obama's approval rating is too low historically for reelection he's in good shape if a Republican like Gingrich (approval rating 27%) gets the nomination. Moreover, he'll hurt GOP candidates nationwide in an environment in which Republicans should do remarkably well.
Romney, Gingrich and Santorum all have big weaknesses but Romney remains the most electable. In reality, the GOP really needs a better candidate so perhaps a Gingrich win is good in a way if the convention ends up split and can settle on someone else.