Marco Rubio was supposed to be the future of the Republican party: young, intelligent, charismatic — and electable enough to worry Democrats.

Instead, he ended up illustrating just how much trouble his party is in.

Rubio suspended his campaign Tuesday, after a humiliating defeat in his own home state of Florida. Far from being the last Republican standing, he won't even be the last establishment Republican standing in a primary that generally hasn't been favorable to establishment Republicans. (Ohio Governor John Kasich, who at least managed to win his home state, remains in the presidential race alongside Donald Trump and Ted Cruz.)

It's easy to write off Rubio's campaign as doomed to fail — an establishment candidacy in an anti-establishment cycle. But Rubio and his party weren't exactly blameless victims of history. Both of them failed, for months, to realize they had to actually work to keep the nomination out of the hands of Trump (and Cruz). And when they did respond to Trump, they did it in the wrong way and far too late.

The party might recover from Rubio's defeat. Rubio might not.

It's hard to win a nomination when you don't win primary states

Only a few candidates have managed the nomination without winning either the Iowa caucus or the New Hampshire primary. But for some reason, that was the course to the nomination that Rubio's team charted.

This isn't for the reason you might assume — that Rubio wasn't popular with the Republican base. He was absolutely unpopular with many of the most conservative voters, and with the conservative movement, after picking a fight with conservatives over immigration reform in 2013 and losing. But Rubio's relatively strong finish in states like Iowa and South Carolina indicates that he did have some sort of constituency among Republican voters — especially those who described themselves as "somewhat conservative," a group he actually won in Iowa.

But it's that phrase "relatively strong finish" that's the problem here. Rubio's political skills — both on the campaign trail and in debates — were supposed to be tremendous. But when it counted, he turned out not to be as good at either as he was supposed to be.

The Rubio campaign bet that in 2016, individual campaign-trail appearances mattered less than what voters were seeing on television. They spent their money in Iowa and New Hampshire on ads, while hunkering down in states with later primaries for what they called a "national strategy."

As a result, Rubio simply didn't spend as much time on the trail in Iowa and New Hampshire as candidates typically do. It sometimes didn't even look like he was trying to win them — because he wasn't.

Instead of trying to win Iowa and New Hampshire to gather momentum for the rest of the race, the Rubio campaign used a different momentum tactic: setting low expectations for Rubio's performance, then taking advantage when those expectations were exceeded. They called it the "3-2-1" strategy — placing third in Iowa would allow them to place second in New Hampshire, which would give them the momentum to win South Carolina.

It briefly looked like this would work. Not only did Rubio get more voters than he was expected to in Iowa, but he came only two points behind second-place Donald Trump. But Rubio ruined his own momentum with a disastrous performance in the debate between Iowa and New Hampshire, in which he responded to Chris Christie's attack that Rubio robotically repeats his talking points by...robotically repeating his talking points:

He fell to fifth in New Hampshire. And by the time he rebounded in South Carolina, the press — the key constituency that was needed to make the 3-2-1 strategy work — began to get wise to his campaign's attempts to spin third-place finishes as victories.

Rubio's momentum was supposed to be 3-2-1; instead, his record shows his failure to gain traction:

3-5-3-2-2-3-2-3-3-3-3-3-3-1-3-3-3-3-4.

By the end of his campaign, Rubio had even moved away from the campaign-trail demeanor and stump speech that made him so appealing. He somehow decided that the right way to take on bully Donald Trump was to bully him right back — except that Rubio never made a credible bully.

When Rubio insinuated that Donald Trump had a small penis, Trump amplified and rebutted the criticism during a debate — Rubio got all the blowback for his innuendo, with none of the benefits. But when Trump called Rubio "little Marco," it stuck.

Instead of destroying Trump just as Christie destroyed him, Rubio destroyed himself all over again — damaging his support with the campaign media, one of the few constituencies he had left.

It's hard to be the establishment candidate when the establishment doesn't support you

In the early months of the 2016 campaign, most people inside and outside the Republican Party figured the primary would come down to two candidates: an "outsider" candidate like Ted Cruz, Ben Carson or Donald Trump, and an "establishment" candidate like Jeb Bush or Marco Rubio.

That theory began to fall apart toward the end of 2015, largely because the continued dominance of Donald Trump in the polls forced people to throw all their theories of the race out the window.

But the Republican establishment didn't react to Trump in the way people expected.

A lot of people expected that the Republican establishment would react to the prospect of a Trump vs. Cruz presidential race — a race between a candidate who openly flouted them and a man they despised — by consolidating behind a single "establishment" candidate.

GOP donors could give that candidate the funds to stay in the race until Trump eventually faded; as an added benefit, they wouldn't be hurting their own cause with expensive ad buys from one establishment candidate attacking another.

And the candidate it made the most sense to consolidate around was Marco Rubio — the only establishment candidate who was garnering double-digit support in the polls in late 2015.

That is not what happened at all. Not only did other establishment candidates like Bush and Chris Christie stay in the race, but they kept spending money to attack each other rather than going after Trump. Jeb Bush's super PAC Right to Rise raised more than $100 million, and spent $20 million of it attacking Rubio.

Only after the Iowa caucuses did the party establishment begin to coalesce around Rubio. And only after Bush dropped out in the wake of a poor performance in the South Carolina primary did they begin to do so in earnest.

Rubio's weird failure to consolidate the establishment behind him was even more evident when it came to endorsements. When Lindsey Graham dropped out of the race, he endorsed not his fellow senator Rubio (who he'd worked with on comprehensive immigration reform in 2013) but Bush. Even after Rubio validated his candidacy with a strong third-place finish in the Iowa caucuses, his fellow senators (with the exception of South Carolina's Tim Scott) conspicuously held off on endorsing him.

It's clear that the Republican establishment badly misjudged the 2016 race by failing to get behind a single candidate. But that still doesn't explain why Rubio failed to unite the party elites behind him.

Perhaps they were worried by vague but persistent rumors about ethics problems (rumors that the Bush camp definitely had an eye on as part of its anti-Rubio strategy). Maybe even GOP donors who weren't committed to Bush felt too much loyalty to the Bush family to throw down on behalf of his young rival. Perhaps they worried that Rubio would lose any chance he had of appealing to the party's base if he was being too obviously supported by Republicans in Washington.

Whatever the reason, Rubio never managed to clear the "establishment lane" for himself.

What's next for Marco Rubio?

Rubio's Senate seat is up in November. But he's sworn up and down he doesn't want to return to the Senate. And his career there is basically over anyway.

Unlike his Senate colleague and fellow 2016 candidate Ted Cruz, Rubio was a relatively popular senator before his presidential run — gaining respect from members of both parties.

But if America learned anything about Marco Rubio from his run for president, it's how much he hated being in the US Senate.

Rubio's poor attendance in the Senate became one of the key lines of attack against him, used by both Jeb Bush and Donald Trump. Voters didn't sour on him, but some in the political establishment clearly did. A Washington Post headline from October said it all: "Rubio gives up on Senate: 'He hates it'".

That raises questions about what Rubio does want to do next. It will be at least four years before he can run for president again — and while the Republican establishment is often more favorable toward candidates on their second presidential run, it's not clear whether he can clear the mysterious obstacles that stopped Rubio from being the single establishment choice in 2016.

He's still young. He's still talented. And he has close relationships with some key Republican policy wonks. But it's not clear what job fits those skills as well as "presidential candidate" does. And if Rubio wants to be a presidential candidate in 2020 or 2024, he'll probably have to find a way to stay in the spotlight until then.