For over a year now, Marco Rubio and his substantial cheering section have been trying to ignite Marco-Mentum without notable success. Well, they finally made fetch happen – and just in the nick of time.

In the run-up to the Iowa caucuses, there was clearly something stirring. Trump’s numbers were falling; Rubio’s were rising. Just as in 2012, there was a late-breaking surge for the rising candidate. It’s just that this time, the rising candidate was a media darling rather than a factional protest candidate of the social-conservative right.

The first interesting question is: why? Rubio did not invest in the kind of ground-game infrastructure in Iowa that Cruz did. The things that might be appealing about him – youth, glibness, media support – have been true for some time. Why the late surge?

I’m reluctant to believe that skipping the final GOP debate actually made that much difference – but maybe it was a fatal error? Maybe merely showing the voters a field without Trump made it more plausible to distinguish among those alternatives rather than see them as a non-Trump mass?

Maybe this really was a case of “the party hasn’t decided yet” and it finally made up its mind. Mainstream GOP voters in Iowa simply weren’t being told by their betters who they have to choose (as they were told in 2012), and so they didn’t choose until the last minute. And of the remaining non-Trump, non-Cruz choices, Rubio was actually the most appealing.

Maybe all the Trump hype (which I participated in) actually energized those non-Trump, non-Cruz voters to show up and represent the mainstream of the party. Cruz’s Iowa victory is a victory for organization, a plan well-executed. Both Trump’s disappointing second-place showing and Rubio’s strong third-place showing, by contrast, were the product less of careful planning than of enthusiasm. High turnout was supposed to help Trump. Instead, it helped his opponent.

So what happens now?

Before the late surge for Rubio, I argued that Trump was in the dominant position. He could lose Iowa to Cruz, but in a Trump-Cruz race Trump had the distinct upper hand. And if Trump won Iowa, he would be favored to win New Hampshire, South Carolina, Nevada, and then practically run the table.

Rubio’s strong third-place showing clearly changes that calculus. Rubio’s mainstream opponents in New Hampshire – Bush, Kasich and Christie – will face a dilemma. If they turn their fire on Rubio, they risk facilitating a modest Cruz surge in New Hampshire, and setting up a Trump-Cruz contest for the South. If they lay off Rubio, then he should be able to capitalize on his Iowa results to finish a strong second in New Hampshire, which would decisively end all of their campaigns. Nonetheless, I would expect all of them to come under heavy party pressure to pursue the latter course, and focus their fire on Cruz. As a consequence, if Rubio doesn’t come in second in New Hampshire, that should count as a disappointment.

But the real state to watch is South Carolina. Rubio picked up the (presumably long-arranged) endorsement of Senator Scott. His numbers were moving modestly upward in South Carolina before Iowa. And both Bush and Carson, who had meaningful support in the last batch of polls, would be expected to decline. If their voters go to Rubio rather than to Cruz (I assume they won’t go to Trump), then he has a real chance to win the state.

Rubio’s situation is comparable, in different ways, to McCain’s in 2008 and Bill Clinton’s in 1992. Like Clinton, he’s the young, up-and-coming candidate who was tagged early on as the likely winner before he’d actually demonstrated the ability to win actual votes. And, like both Clinton and McCain, his main opposition (Tsongas and Brown in Clinton’s case, Romney and Huckabee in McCain’s) are viewed as less-electable and less-acceptable to the party mainstream. Having proved himself a viable alternative, the party may well rally around him, and muscle him to victory.

But Rubio’s opposition is also considerably better-resourced than either Clinton’s or McCain’s was. Cruz has plenty of money and a strong organization. He planned for a long contest from the beginning. Trump has his own fortune (which he hasn’t had to spend yet) and has already demonstrated the ability to energize large numbers of voters.

Moreover, both Cruz and Trump have an argument on their side. Neither is a pure factional candidate, the way Huckabee was, or an incoherent protest, the way Gingrich was. On both foreign and domestic policy, there are real, meaningful differences with Rubio that have been far from irrelevant to their success so far.

If that argument is joined, there’s reason to believe that Rubio will actually have to keep fighting in order to win. We’ll soon see just how much fight he has in him.