Who knows whether or not it's too late for Huntsman to pull an upset in New Hampshire. But it's probably too late for Romney to make a compelling argument, when and if Romney's the nominee, that he's going to be a uniter for the country.
Huntsman raised a point that probably hasn't been much made since the 1970s: the idea of service to one's country over ideology. I can already see the anti-Romney attack ads writing themselves. Can't you? The sheer pettiness of the modern GOP has become insufferable.