Sen. Marco Rubio (R-Fla.) arrives for a town hall meeting in Nashua, N.H. (Charles Ommanney/The Washington Post)

In 2012, Sen. Marco Rubio had President Obama pegged: a guy who “has no idea what he’s doing.” As recently as December, Rubio described Obama as “overwhelmed” by the threat posed by the Islamic State.

Those characterizations of an in-over-his-head president sound different from the argument Rubio made, over and over again, in his now-infamous debate performance Saturday night: that Obama is, in fact, so deft and in command that he is systematically altering the essence of America.

While Rubio drew mockery for repeating the lines, they highlighted the Republican candidate’s difficulty in distinguishing himself from a president with whom he has a lot in common biographically but who is loathed by most of his party.

Like Obama, Rubio, 44, is a young first-term senator who arrived in Washington fresh out of a state legislature. Obama, when he ran in 2008, spoke often about his African father’s journey to America; Rubio likes to tell the story of his Cuban immigrant parents on the campaign trail.

And for months, Rubio has been peppered with questions and attacks centering on whether he is the Republican version of Obama. Curious voters have asked him about the similarities. The topic has been raised in interviews. And lately, his rivals have been making the comparison in a negative light more intensely than ever.

Rubio greets people at a Super Bowl watch party Sunday at Ultimate Sports Academy in Manchester, N.H. (Charles Ommanney/The Washington Post)

“We tried a rookie senator with no experience, and we can’t afford that risk again,” says an advertisement from Right to Rise USA, a super PAC supporting former Florida governor Jeb Bush. “Marco Rubio simply isn’t ready for the biggest job in the world.”

Rubio’s campaign says he has responded to such comparisons consistently from Day One.

“Our primary response to this question has never changed,” said Rubio spokesman Alex Conant. “Obama isn’t a failed president because he served in the Senate. He’s a failed president because his ideas are really bad.”

Rubio is leaning heavily into the argument he advanced at Saturday’s debate: It is not Obama’s youth or inexperience that makes him a bad president, but his willful reshaping of the country’s identity.

“People keep [saying], ‘Why do you keep saying the thing you’re saying about Obama trying to change America?’,” Rubio said at a town hall here Monday. “I’m going to keep saying that a million times.”

The comment he was referring to was one he repeated, almost word for word, four times at Saturday’s debate.

Rubio poses for a “selfie” outside the Barley House Restaurant on Monday in Concord, N.H. (Charles Ommanney/The Washington Post)

“Let’s dispel once and for all with this fiction that Barack Obama doesn’t know what he’s doing,” Rubio said in one rendition. “He knows exactly what he’s doing. Barack Obama is undertaking a systematic effort to change this country, to make America more like the rest of the world.”

Some of what Rubio is saying now seems at least partly at odds with what he said before he was a candidate for president.

Stumping for Mitt Romney in 2012, Rubio framed the election this way: “This is a choice between a guy that has no idea what he’s doing and a guy that does.”

Asked how that squares with what Rubio says now, Conant responded: “Obama has no idea how to grow the economy or make the world safer. But he knew exactly what [he was] doing when he passed Obamacare, Dodd-Frank and the Iran deal — those did not happen by accident. He is trying to make America look more like the rest of the world.”

Rubio has also argued that he entered the Senate and the presidential campaign with more experience than Obama, showing a desire to size up the president’s résumé next to his own.

During a campaign swing though Iowa in July, Rubio argued that Obama had been a “backbencher” in the Illinois legislature, while Rubio arrived in the Senate after serving as speaker of the Florida House. He also pointed out that he had served in the Senate longer than Obama had when he declared his campaign for president in 2007.

“This president has not been a failure because he was a senator,” Rubio said then. “This president has been a failure because he has failed on the key questions of presidential leadership.”

Rubio also said that Obama’s ideas are “outdated.” He called the president a “divisive figure” who decided to “pit Americans” against one another.

Here in New Hampshire, Rubio has faced relentless attacks from two governors running for president and from their allies.

Bush said last week that “the challenge” with Obama, “an extraordinarily gifted man, very smart, great orator, is there was nothing in his background that would suggest he could lead, and it turns out he hasn’t.” Bush said it was “fair game” that Rubio and Ted Cruz, another freshman senator running for president, should face scrutiny as a result.

New Jersey Gov. Chris Christie, who mocked Rubio for using the same talking point repeatedly in Saturday’s debate, also compared his experience level with Obama’s.

“We’ve watched it happen, everybody, for the last seven years,” he said. “The people of New Hampshire are smart. Do not make the same mistake again.”

What happens in New Hampshire on Tuesday night could determine whether Rubio will have to endure a fresh round of such attacks. Aside from Bush, Christie and Ohio Gov. John Kasich, Rubio’s main competitors are Cruz and Donald Trump, who has never held elective office.

For now, Rubio is content repeating himself.

“Voters across the country and especially here in New Hampshire got to hear me say repeatedly the truth: that Barack Obama is trying to redefine the role of government in our country and America’s role in the world,” he told CBS News on Monday.

Ed O’Keefe in Tilton, N.H., contributed to this report.