Santorum is going to be
crushed by Obama, should he be the nominee. Gingrich being in or out has nothing to do with Santorum's chances, since Santorum is the least likely second choice of the Gingrich voter (I am one).
It would be incredibly reckless to nominate Santorum, but, since he is getting crushed by the Catholic vote in the Midwest, I don't think there's much chance of that happening anyway.