Ezra Klein believes that the candidate's surge says very little about him:
Santorum’s finish doesn’t say much about his ideology, or his campaign skills, or his endorsements. Quite the opposite, in fact. In a race where a large number of anti-Romney voters were desperate to find a candidate, Santorum was unable to attract significant support until the very end, when the anti-Romney vote literally had nowhere else to go. If he had been a better candidate, he would have crested earlier.
That's a bit dismissive of Santorum's dogged, old-school, truck-based campaign, which, to my mind, was exemplary and deserves praise. Ditto Santorum's "concession" speech: moving and smart, compared with Romney's deranged recitation of "America The Beautiful". But I suspect Ezra's right. In this game of musical chairs, if the music had stopped earlier, the nod would have gone to Newt or Ron. But that's politics. Timing is everything.