Image copyright Getty Images Image caption Marco Rubio was mocked for his allegedly robotic delivery

It was the morning after the debate disaster. Marco Rubio had received an on-stage evisceration on Saturday evening from Chris Christie, and less than 12 hours later - at a school cafeteria in Londonderry, New Hampshire - he started trying to pick up the pieces.

After apologising to the crowd for being more than 30 minutes late, and joking about the evening's Super Bowl, the Florida senator launched into his standard campaign stump speech, complete with references to his parents' immigration from Cuba and his middle-class upbringing.

He even riffed on a line he had repeated four times when flustered on the debate stage on Saturday - the one mocked by Mr Christie as a "25-second sound bite" and relentlessly replayed on US news programmes and social media.

"I'm going to say it again," Mr Rubio told the crowd of nearly a thousand. "The reason why these things are in trouble is because Barack Obama is the first president, at least in my lifetime, that wants to change the country."

Those may have been words he has used for months on the campaign trail - but this was no ordinary morning.

Earlier in the week, it appeared as though Mr Rubio was on the verge of gaining the upper hand in the race for the Republican nomination, thanks to a surprisingly strong third-place showing in the Iowa caucuses.

Endorsements from former presidential competitors and prominent politicians were rolling in.

A positive debate performance on Saturday, one on a par with his usual polished efforts, would have left him well positioned to take on frontrunners Ted Cruz and Donald Trump in the days ahead.

Damning verdict

But Mr Christie, with his sharp attack on Mr Rubio's leadership experience and propensity for too-polished answers, knocked the Florida senator off his game. On Sunday morning, the debate verdicts were in - and they were very bad news.

"Choke!" blared the headline of the Boston Herald, over a photo of the senator. "Marco Rubio crashed and burned," reported Politico.

Image copyright Reuters Image caption Chris Christie (left) rounded on Marco Rubio during Saturday's candidates debate

Outside the school, two men - working for a liberal political action committee - paraded around in robot costumes, mocking what they said was Mr Rubio's robotic delivery of canned lines during the debate.

Inside the venue, even Mr Rubio's supporters expressed concern.

"Not one of his better moments," said Monica Mahoney, of Londonderry. "It seems like he got a little flustered. It happens to the best of us."

She added, however, that she hoped a little adversity might make him a stronger candidate.

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A supporter from nearby Manchester expressed surprise Mr Rubio had been unprepared for Mr Christie's fusillade, which had been telegraphed for days in advance.

"I don't have an answer for that," he said. "I was disappointed in his performance."

What could be more troubling for Mr Rubio is that, according to a recent poll, 30% of New Hampshire Republicans are still trying to decide for whom they are going to vote on Tuesday.

If that is the case, his halting performance came at a critical moment in the campaign.

"It's almost embarrassing for him," said Ann Barnes, an undecided voter from Amherst, New Hampshire, who came out with her husband and daughter to see Mr Rubio speak.

"I think he was really rattled by Christie, and I don't know that he ever really recovered."

Further attack

A few hours later and 30 miles to the east, in Exeter, Mr Christie was still laying on the rhetorical abuse.

"This is not a game, everybody," the New Jersey governor said during a rally at a local pub. "This is not just something where a guy makes a good speech and looks good in a suit, so let's make him president of the United States.

"It doesn't matter that I like Marco Rubio and think he's a good guy.

"He's not ready. And last night when the heat went on, he proved he was not ready."

Although she was there for lunch and not to see the governor, Carol Johnson, of South Hampton, nodded in approval.

"I like Christie," she said. "He's just down to earth."

She said she had been considering Mr Rubio, but the previous night's debate had given her doubts.

"He's a nice guy," she said. "He just doesn't have the experience."

Image copyright Getty Images Image caption Mr Rubio sparkled in a school rally in Derry

Up until now, Mr Rubio has been able to overcome his lack of a lengthy political record - he has served only five years in the US Senate and was a Florida state legislator before that - by wooing voters with his personal narrative.

Just two days earlier, at a middle school in Derry, New Hampshire, those skills were on full display.

When he spoke about education, he told the crowd he had struggled paying off six-figure student loans after university.

When the topic turned to preserving social security retirement benefits, he said the money was a lifeline for his mother.

The Medicare health insurance programme for the elderly, he said, had provided care for his father when he had battled terminal cancer - and he would make sure it stays solvent.

He said he identified with Americans struggling in today's economy.

"We're going to take our message to those who live paycheque to paycheque because I lived paycheque to paycheque," he said. "I know what it's like."

In the audience were a group of Cuban-Americans who had travelled from Miami to volunteer for the Rubio campaign, and they spoke of him and his family in glowing terms.

"You see the nice suit and the speeches, but they're just sincere, good people," Lisa Lorenzo, who attends church with the Rubio family, said. "They're just normal people who happen to have the gift to serve the community."

A presidential campaign is essentially a sales pitch, and the 2016 race for the Republican nomination is no different.

Some candidates, such as Mr Christie, Jeb Bush and John Kasich, are selling their experience running state governments. Donald Trump is offering his no-nonsense business experience. Ted Cruz is running on his conservative ideological purity.

Selling himself

More than any other candidate, Marco Rubio is selling Marco Rubio.

At his speech Friday night, Mr Rubio's supporters listed his personal attributes - his charisma, his broad appeal and, most importantly, his electability - as the reasons they were drawn to him.

"He's so hopeful," said Carol Lupima. "It's his roots, it's who he is, it's who he's become. I was really impressed with that."

Image copyright EPA/Reuters Image caption Ted Cruz and Donald Trump were first and second in Iowa

David Anelundi, of Derry, said he saw the Republican race boiling down to a battle between Mr Cruz, Mr Trump and Mr Rubio.

"I was leaning towards Marco, but I am leaning towards him more now that he's done very well in Iowa," he said. "I think he's a legitimate candidate that we can vote for."

If it seemed clear on Friday that a three-man battle for the Republican presidential nomination was about to unfold - the outlook has become a bit more muddled after Mr Rubio's Saturday night stumbles.

A veneer of electability can disappear in a moment. A personal narrative compelling at one point can later appear worn and overplayed.

The Florida senator has obvious political skill. He still may perform well in the New Hampshire primaries, potentially knocking Mr Christie and others out of the race.

New Hampshire voters are noted for their fickleness and propensity for last-minute decisions, however, and Mr Christie may have given them a reason to take another look at the Republican presidential field.