Sen. Marco Rubio (R-Fla.) trails Republican presidential candidate Donald Trump significantly but is running ahead of former governor Jeb Bush (Fla.) and Gov. Chris Christie (N.J.). They are pitting their experience against the Florida senator’s record. (Alice Li,Dalton Bennett/The Washington Post)

Marco Rubio’s robotic debate performance Saturday night sparked an all-out offensive on the campaign trail here Sunday over his authenticity and experience, momentarily halting the momentum of the senator from Florida and further muddling the presidential nomination battle.

Just two days before the New Hampshire primary, Rubio drew mockery for repeating a rehearsed line four times during the Republican candidates’ debate, even after New Jersey Gov. Chris Christie had ridiculed him for being a talking-point machine.

Rubio received scathing reviews on the Sunday talk shows and was needled by some of his opponents. On Twitter, he earned the moniker “Rubio bot.” Clips of the debate played repeatedly on cable news and were watched hundreds of thousands of times on YouTube.

The episode interrupted Rubio’s week-long effort to build on his impressive third-place showing in the Iowa caucuses and consolidate donors and party officials behind him. It also appeared to give new life to the struggling candidacies of Christie, former Florida governor Jeb Bush and Ohio Gov. John Kasich, while improving Donald Trump’s chances of winning the New Hampshire Republican primary.

The battle continues in New Hampshire as candidates fight tooth and nail to take home the state. The Post’s David Weigel walks through what it will take to win the New Hampshire primary. (Dalton Bennett/The Washington Post)

The fallout for Rubio over the long term could be severe. His GOP rivals argued Sunday that the debate undercut the central case for Rubio’s candidacy — that his political agility and youthful, charismatic persona make him best positioned to challenge the Democratic nominee.

And they claimed a renewed — and seemingly justifiable — rationale to soldier on past New Hampshire, which would mean that the mainstream Republican vote would probably continue to splinter among several candidates.

“The whole race changed last night,” Christie said Sunday on CNN. “There was a march amongst some in the chattering class to anoint Senator Rubio. I think after last night, that’s over. I think there could be four or five tickets now out of New Hampshire because the race is so unsettled now.”

Bush also sounded reinvigorated by the difficulties of the otherwise polished Rubio, his onetime Florida protege who has overshadowed him all year. “I envy the people that have, you know, message discipline, to say the same thing over and over again,” Bush told a standing-room-only crowd in Salem. “Sometimes it doesn’t work out.”

Kasich, buoyed by a solid debate performance, refused opportunities Sunday to go after others and instead asked New Hampshire voters to affirm on Tuesday his “unifying positive message.”

Rubio, for his part, came out swinging in a series of events. He was defiant as he defended his debate-night talking point that portrayed President Obama as a wily operator who has succeeded in enacting a liberal agenda.

“I’m going to say it again,” Rubio told a gathering in Londonderry. “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.”

Nonetheless, the debate haunted Rubio on Sunday. In the parking lot at his campaign stop in Hudson, someone placed photo­copies of the Boston Herald’s front page — which showed a picture of Rubio with the headline “Choke!” — under the windshield wipers of cars.

Trump has held a dominant lead in the polls in New Hampshire for months. There was a growing sense on the ground in recent days that Rubio might surf a wave of buzz and goodwill to contend for the top spot, but party strategists said the debate probably closed whatever opening may have existed.

Many of the candidates met crowds swelling into the hundreds and even thousands as they barnstormed the state Sunday, fielding questions at town hall meetings and pressing the flesh at diners and pubs. Advisers to the campaigns saw Trump as the favorite but said the race for second place was anybody’s game, citing New Hampshire’s famously fickle and late-deciding electorate.

“It’s unbelievably volatile,” said Steve Duprey, an unaffiliated Republican National Committee member from New Hampshire. “This is the most hotly contested race I’ve seen since the 1976 Ford-Reagan primary.”

The final days in New Hampshire have signaled an unmistakable evolution in the Republican race: For the first time since the summer, it is not revolving solely around Trump.

The campaign has matured, with the non-Trump candidates building their own coalitions, driving their own messages, drawing differences with one another and making their own headlines.

The run-up to Saturday’s debate was unusual in its absence of a Trump controversy. Indeed, he has been a sporadic presence on the campaign trail in New Hampshire.

“For the first time in this entire election cycle, a candidate other than Donald Trump is actually able to get their message out,” said Todd Harris, a senior adviser to Rubio.

Sen. Lindsey O. Graham (R-S.C.), a vocal Trump critic and Bush booster, said Trump’s ­second-place finish in Iowa behind Sen. Ted Cruz of Texas sapped some of the energy around him.

“He went from being the big-man winner to a whiner,” Graham said.

Trump, too, acknowledged a new dynamic. “They’re getting better,” he said of the other candidates after the debate. “But I’m always in the center. I’ve always been in the center from Day One.”

In a departure for a candidate who typically jumps at the chance to puncture his opponents, the businessman resisted critiquing Rubio in post-debate interviews.

“He’s been hit very hard on the Twitter,” Trump said late Saturday night. Wincing, he added: “I don’t know. I mean, I don’t want to comment on anybody else’s performance, because I actually have a very good relationship with Marco.”

Trump may stand to gain from Rubio’s longevity in the upper tier because the senator prevents Cruz from uniting the right.

Trump labored through two subdued campaign stops Sunday afternoon, forgoing his typical bomb-throwing against his chief opponents during a rally of about 1,000 people in Plymouth, N.H. Trump’s most upbeat appeal came when he reminded voters of the importance of showing up.

“You guys better vote for me,” he said with a smile. “I don’t need your money, I need your vote!”

For Rubio, there were glimmers of recovery. His unapologetic debate answer defending his opposition to abortion rallied social conservative leaders to his side and helped induce what aides said was $600,000 in online fundraising.

Charlie Dancause, 63, a retired postal worker and Navy veteran, watched Rubio campaign in Londonderry and was impressed.

“I thought he got killed,” Dancause said, but “he bounced back. And today he’s smiling. He’s in with the crowd. He takes a licking and keeps on ticking. That’s what a politician needs to do!”

In his post-debate analysis, Harris looked ahead to a general election featuring Rubio as the party’s standard-bearer.

“We took the fight to President Obama,” Harris said of Rubio’s repeated talking point. “The media may not like it, but you know what? We’re going to do the same thing tomorrow and the next day and the next day.”

Some Rubio’s allies said they were bracing for a long slog.

“Marco is in a very strong position to be the nominee,” said Sen. Patrick J. Toomey (R-Pa.), who endorsed Rubio last week.

“It’s going to be a fight, it’s going to be a battle, it’s going to take a while to put it all to bed, I suspect, but he’ll do it,” Toomey said.

James Hohmann in Londonderry, Sean Sullivan in Hudson, Jose DelReal in Plymouth, Michael Kranish in Concord, Ed O’Keefe in Salem and David Weigel in Peterborough contributed to this report.