Rubio appeared seriously rattled by the exchanges at the final Republican presidential debate before Tuesday's New Hampshire primary. He repeatedly tried to fight off Christie -- without much effect -- by shifting the focus to President Barack Obama and the Democrats.
Donald Trump, meanwhile, was booed during an exchange with Jeb Bush. The billionaire then turned on the audience, suggesting it was made up of party figures and big donors and was therefore biased against him -- and the booing escalated.
But it was Christie, who is making a do-or-die last stand in New Hampshire, who proved relentless on the debate stage, blasting Rubio as someone who delivers soaring speeches but has never made a consequential decision in his political life.
"Marco, the thing is this," Christie said at the ABC debate at St. Anselm's College in New Hampshire. "When you're president of the United States, when you're a governor of a state, the memorized 30-second speech where you talk about how great America is at the end of it doesn't solve one problem for one person," Christie said.
Christie also slammed Rubio's poor attendance record in the Senate.
"That's not leadership, that's truancy," Christie said.
Rubio tried to blunt Christie's attack by saying that he had not wanted to leave the campaign trail to return to New Jersey before a major snow storm last week. The senator then spoke of the aspirations of the American people.
But Christie had none of it, refusing to let Rubio wiggle out of the way of his assault, playing on a narrative advanced by Rubio's opponents that he has simply learned a fluent stump speech and deploys it every time he appears in public.
"There it is, the memorized 20 second speech," Christie told the crowd.
Rubio did find a firmer footing later when the conversation turned to foreign policy. But the ferocious exchange with Christie, the most combative pre-meditated assault of the 2016 season, is likely to be played over and over again on news shows in the run-up to the primary.
While it was was not immediately clear whether the showdown would seriously harm Rubio's chances on Tuesday, it did appear to have the potential to dent his momentum after a stronger-than-expected third place finish in the Iowa caucuses. A CNN/WMUR poll released on Friday, meanwhile, found Rubio in second place in New Hampshire.
Former Florida Gov. Jeb Bush added to the Rubio criticism, saying that Americans shouldn't gamble on a candidate who doesn't have executive experience.
"Marco Rubio is a gifted politician and he may have the skills to be president of the United States," Bush said.
Bush then compared Rubio to Obama, who entered the White House without executive experience.
Carson vs. Cruz
Ben Carson, meanwhile, laid into Ted Cruz after a skirmish in the aftermath of the Iowa caucuses.
CNN reported on Monday that the retired neurosurgeon planned to go home to Florida after the Iowa caucuses, rather than flying straight to New Hampshire or South Carolina, where the next primary contests are held. His aides emphasized that he is not suspending his campaign -- rather, just briefly going home to "get a fresh set of clothes."
But the Cruz campaign reacted to the news by incorrectly telling precinct captains -- while the caucuses were still taking place -- that the move signaled Carson would be dropping out of the race.
Carson said Saturday that the actions of Cruz's campaign were an example of "Washington ethics" as he tried to portray himself and not Cruz as a true outsider candidate.
Cruz tried to defuse the clash by saying, "Ben, I am sorry."
The debate began on a bizarre note with several candidates, including Trump and Carson, apparently not hearing their introduction amid the noise of the crowd at St. Anselm's College. Both stood awkwardly in the wings as other candidates including Rubio and Bush pushed past them. Then Ohio Gov. John Kasich apparently was not introduced at all, and had to be called on stage by moderator David Muir.
Trump back on stage
Trump is back on stage after boycotting the last GOP debate over a dispute with Fox News
Bush, who has been bullied by Trump throughout the campaign, appeared to get the better of the real estate mogul in an exchange about eminent domain, a practice by which a government or private entity can appropriate land or property in return for payment of compensation.
"How tough is it to take property from an elderly lady," Bush asked, sparking a furious response from Trump.
It was perhaps Bush's strongest moment so far in his long-simmering confrontation with Trump, and it was on an issue that often preoccupies voters in "Live Free or Die" New Hampshire.
The latest CNN/WMUR tracking
poll of likely Republican primary voters published Friday found Trump dominating the race with a fierce battle for second unfolding between Rubio at 17%, and Cruz and Kasich, who are tied for third place with 13%. The three, however, are within the poll's margin of error of 5.8 percentage points.
Bush and Christie, meanwhile, are trailing in the low single digits.
One candidate not taking part on Saturday night is Carly Fiorina
. The former businesswoman did not satisfy polling criteria set by ABC News and says the game was rigged against her because she beat Christie and Kasich in Iowa, and they will be on the stage and she won't.
Christie, Kasich and Bush know there may be a spot for only one of them as the race leaves New Hampshire on Tuesday night, so time is running out.
North Korea missile test
The candidates seized on a long-range missile test by North Korea minutes before the debate opened to portray the Obama administration as weak on foreign policy and to promise to have a much more robust posture in the world.
Cruz used the test to argue that the administration's nuclear deal with Iran was foolhardy because he said it would lead to Tehran getting the same kind of nuclear arsenal that Pyongyang currently had.
And Christie used the test to slam Obama as "so weak," adding that Hillary Clinton, who is seeking to succeed Obama, "would be even weaker."
Rubio also found himself under a withering attack from Christie over immigration reform and the legislation he backed in the Senate for a comprehensive overhaul of the system that he eventually repudiated.
"The legislation passed but it had no support," Rubio said, trying to explain his position on the issue which has become a vulnerability for him in the Republican primary amid grass-roots fury over illegal immigration.
Christie piled on again, accusing Rubio of abandoning his legislation when it became clear it would be a political liability -- a move he said was typical of Washington.
"It is abundantly clear that he didn't fight for his legislation," Christie said.