James: If Romney narrowly loses tonight, there is certainly a rationale for him to continue. But I think his path to the nomination becomes a lot harder. He is beating McCain among conservatives, but not by the same margin that McCain is winning among moderates. After tonight, McCain is going to further consolidate the moderates. It isn’t clear that Romney will be able to further consolidate the conservatives.
Also, consider the media boost McCain got from a fourth-place showing in Iowa (albeit just shy of third place) and a little better than three-point win in South Carolina. A win in Florida sends him into Super Tuesday with free media and a probable infusion of cash, eroding Romney’s biggest advantages.
Phil: I agree that even a victorious Romney will have a tougher slog than McCain. But McCain needs to wrap this thing up before he goes broke. Romney is much better positioned to afford a slower war of attrition. And if there is any thinning of the conservative herd, though I don’t think that’s likely, Romney could benefit even more than McCain would by consolidating the GOP’s moderate minority.