Rubio is not a Republican Obama. And that’s his problem.

One of the most frequent refrains among Republican voters this year is that Barack Obama was tragically unprepared for the office when he was elected president. And this, more than anything else, is proving to be a problem for Marco Rubio, whose resume in government closely mirrors the president’s, and who has been compared to Obama from the moment he entered the national consciousness in 2010.

Most often, Rubio tries to head off this comparison by repeatedly and acidly berating Obama, as if desperate to get across that, despite the obvious parallels, he’s really nothing like that other guy. “We are not a weak country, and we are not a weak people,” I heard Rubio tell audiences when I spent time with him in Iowa this week. “We just happen to have a weak president.”

A few days earlier, in New Hampshire, he tried a very different tack, telling an audience that “a liberal Democrat would say Barack Obama has been a pretty influential president,” before going on to list Obama’s considerable accomplishments. The message here being that Rubio is like Bizarro Obama — similarly gifted but ideologically opposite.

In fact, it seems to me that Republican fears about Rubio’s youth and inexperience are probably misplaced. His real problem isn’t so much that he closely resembles the candidate Obama was, but more that he doesn’t.

When I interviewed Rubio in April, a few weeks before he announced his candidacy, he previewed for me a pitch that was largely premised on bringing about the same kind of generational transition in Republican politics that Obama had in his own party.

“I believe that the Republican Party has an opportunity in 2016 to do something it hasn’t been able to do in a long time, and that is make the argument that we’re the party of the future, that we are the party that understands the 21st century and understands what it takes to make America great in the 21st century,” he told me.

Back then, of course, Rubio seemed to be drawing a sharp past-versus-future contrast with the two candidates he thought most likely to stand in his path: 62-year-old Jeb Bush and 68-year-old Hillary Clinton.

He wasn’t betting then that his real problem wouldn’t be Bush, but rather Ted Cruz, another first-term, Cuban-American senator, who at 45 is only a year older than Rubio. He wouldn’t have imagined that Donald Trump, with a kind of ghoulishly ageless appeal, would take Rubio’s “make America great” thing and make it his own.

Rubio still makes his generational case, but the meaning now is murkier. When I met up with him in Pella, Iowa, Wednesday, he was speaking in front of a busily designed blue banner, on which were listed a long series of meaningless phrases: “New American Century. Renewed American Values. New American Jobs. Renewed American Education. New American Leadership.” And so on.

Later, in a conversation aboard his campaign bus, I asked Rubio if his generational argument still seemed relevant.

“The generational choice has always been about our ideas, about whether we we’re going to confront 21st-century issues,” Rubio told me. “And the fundamental argument I’m making is the best way to confront 21st-century issues is by applying the principles that made us great to the unique challenges before us now.”

So, I clarified, the new American century was really about returning to the principles of the last American century?

“Actually, the principle of the new American century is to make it even better than the 20th century,” he explained.

Oh. OK.

Rubio enjoyed a sustained surge in the polls in late October, on the strength of a forceful debate performance, after which it seemed he might be able to unify the sizable bloc of Republican voters who aren’t ready to disassemble all government and replace it with the hunger games. But his momentum seems to have stalled in recent weeks, and his strategy in the early states seems opaque.

Now some of Rubio’s rivals are coming at him hard, hoping to peel off some of his support in New Hampshire and Iowa. This week, both Bush and Chris Christie attacked Rubio for being AWOL from the Senate, where he only occasionally drops in these days to vote. (“I’m out there running for president, so these votes start to matter again,” Rubio told me, by way of explanation.)

Republican presidential candidate Sen. Marco Rubio speaks in Clinton, Iowa, on Dec. 29. (Photo: Andrew Harnik/AP)

The most pointed attack on Rubio, however, has to do with his limited experience. Christie, who is within striking distance of Rubio in most New Hampshire polls, repeatedly says that the last thing the country needs is another president who needs “on-the-job training,” someone who will sit down on his first day in the Oval Office and say, “Gee-whiz.”

“He has no experience governing,” Christie told me when I brought up Rubio with him a few weeks ago. “He’s had five years in the United States Senate, and for a good amount of that time he’s been running for president.”

If Rubio is frustrated by the unrelenting questions about his resume, he doesn’t show it. As debate watchers know, he tends to greet hostility from others with something like bewilderment, as if he can’t quite comprehend why such a pointless accusation would even occur to anyone.

“No one over the last five years has shown better judgment or better understanding of the national security issues we face than I do,” he told me. “Gov. Christie can say that, but on my first day in office I’ll be reading the same intelligence reports that I’ve been reading for the last five years, because I’m a member of the intelligence committee.

“I’m prepared to be commander in chief the first minute of the first day in office,” Rubio added, “and I’m not sure he can say that or anyone else on the Republican side can say that.”

I asked Rubio the obvious question: why he thought he was any better prepared to be president than Obama had been in 2008. He gave me the obvious answer.

“I don’t believe he’s failed because he was only a senator for two years,” Rubio said. “He has seven years of presidential experience, and the decisions he’s making today are just as bad or not worse than the ones he made at the beginning.”

To a large extent, Rubio’s viability in the coming weeks probably depends on whether voters who loathe the president accept this answer or not. It depends on whether they decide, ultimately, that Obama was too much of an ideologue, as Rubio argues, or whether, as Christie contends, Obama’s brief career as a legislator simply didn’t prepare him to govern.

It may also depend, to some extent, on whether Rubio can compensate for some of the advantages Obama had that he doesn’t.

On paper, Obama and Rubio present strikingly similar candidacies. Both were state legislators who became celebrated first-term senators. Both represent a demographic shift in the country toward a fast-approaching nonwhite majority. Both rose on the strength of inspiring personal stories and electrifying speeches.

In some cosmic way, Rubio must know that he probably owes his ascendance in national politics to Obama’s. Every party goes looking for its version of the latest model; just as George W. Bush seemed to be the boomer antidote to Bill Clinton, Rubio arrived on the scene just as Republicans were scrambling to find their own personification of youth and inclusivity.

But 2016 is turning out to be nothing like 2008, and Rubio’s candidacy isn’t really much like Obama’s. For one thing, Obama benefited from having the kind of clear foil, in Hillary Clinton, whom Rubio had hoped to face in a much smaller field — older, establishment-backed, shadowed by a sense of dynastic entitlement.

Obama was also fortunate in that he could tap into a powerful constituency inside the party. Clinton needed African-Americans voters, but after Obama proved himself capable of winning in Iowa, those voters swung heavily into his column, changing the electoral math of the primaries. There is no corresponding bloc of Latino voters in the Republican Party, other than in a handful of states.

More to the point, though, Rubio isn’t anything like the fluid politician Obama was in 2008. It’s true that both men are essentially cool characters, more comfortable talking about policy than sharing emotions. But where Obama has always exuded preternatural confidence (some call it arrogance) and an informal, self-deprecating style, Rubio telegraphs caution and uncertainty.

In his town halls this week, Rubio spoke from notes he balanced on a stool, occasionally pausing to find his place, as if manually switching gears in his head. He seemed ill at ease introducing his wife and four (adorable) children, which ought to be the least scripted thing a candidate ever has to do.

After meeting with Rubio last week, a reporter for New Hampshire’s Conway Daily Sun likened him to “a computer algorithm designed to cover talking points.” This was uncharitable, but it’s true that Rubio has a tendency to seek refuge in the well-worn trenches of his rhetoric, to the extent that you sometimes wonder if he has heard the question you’re asking.

When I saw Rubio Wednesday, I referred to his quote about Obama having successfully passed an ambitious agenda, and I asked what lesson he might have taken from that.

“Ultimately, what I endeavor to do is have an economy that empowers individual Americans in their private lives to go out and create jobs and opportunities for themselves and each other,” Rubio said. “My number one obligation as president will be to keep the country safe. And that means rebuilding our military, rebuilding our intelligence capabilities and having a foreign policy with moral clarity.”

I asked him, a bit later, if he might be a hard guy to get to know.

Sen. Marco Rubio listens to a question after speaking in Newton, Iowa, on Dec. 30. (Photo: Andrew Harnik/AP)

“Well, we have a message, and that’s what I’m campaigning on,” he told me. “So, yeah, I mean my campaign speeches are not a stream of consciousness. I’m not out there talking about things that don’t matter.”

I’ve sat with Rubio several times now, just as I spent some time with Obama before he became president. It seems to me that Obama vanquished the doubts about his resume mostly because, rightly or not, he never seemed to doubt the firmness of his own footing. Rubio, on the other hand, is like a man gripping a railing, steady in the moment but afraid to let go.

Actually, if there’s a better analog for Rubio than Obama, it might be John Kerry in 2004. Like Rubio, Kerry was an elusive and insecure candidate, a senator who stepped through every conversation like it was a minefield from his youth in Vietnam.

But Kerry was also the perfect consensus candidate for a riven party — liberal enough to appease supporters of Howard Dean and establishment enough to reassure everyone else. He was both acceptable and electable.

It’s hard to think of any constituency in the Republican Party right now — evangelicals, libertarians, nativists — whose goal in life is to make Rubio our next president, as opposed to Cruz or Carson or Trump. But as I wrote last April, Rubio might still be the candidate who satisfies most of them.

And Rubio is almost certainly one of the most formidable general-election candidates in the field, as any honest Democrat will tell you. Were he to win the nomination, whether against Clinton or Bernie Sanders, he’d have the straight-up generational contrast he wanted from the start, along with the debate stage on which he tends to excel.

No, Rubio isn’t another Obama, for better or worse. But what he is could well be enough.