NEW HAMPSHIRE -- At the final Democratic presidential primary debate of the year, tensions boiled over gun control, how to combat terrorism and the controversy that dominated the past 48 hours: A breach of the national party's voter database.
The debate, hosted by ABC News and moderated by "World News Tonight" anchor David Muir and Chief Global Affairs Correspondent Martha Raddatz, featured some of the most intense sparring yet, between former Secretary of State Hillary Clinton, Vermont Sen. Bernie Sanders and former Maryland Gov. Martin O'Malley.
It began with an apology from Sanders to Clinton for a now-fired campaign employee who accessed some of her proprietary campaign data after a glitch from a Democratic National Committee's computer vendor exposed it.
But that's where the contrition ended.
The attacks flew between the three candidates at the debate at St. Anselm College in New Hampshire, where despite Clinton's sweeping national lead, Sanders remains competitive. The most recent Boston Herald poll found a tight race in the Granite State: Sanders at 48 percent and Clinton at 46 percent.
With just 43 days until the Iowa caucuses and 51 days until the New Hampshire primary, here are 9 moments that mattered at Saturday night's debate:
1. Sanders Says He's Sorry
Vermont Sen. Bernie Sanders kicked off the debate by apologizing to Hillary Clinton for a campaign aide who accessed her campaign's private data. That aide has since been fired.
"Yes, I apologize," he said when asked by Muir whether Clinton was owed an apology. "Not only do I apologize, I want to apologize to my supporters. This is not the kind of campaign that we run."
Clinton responded: "I very much appreciate that comment, Bernie. We should move on because I don't think the American people are all that interested in this."
But former Maryland Gov. Martin O'Malley was having none of it. "For crying out loud, our country has been attacked," he said, pointing to issues that he said were more important. "Instead, we're listening to the bickering back and forth."
Sanders' remarks came after a bug in the firewall of the Democratic Party's voter data software allowed four Sanders staffers to access files belonging to the Clinton campaign.
2. Clinton Calls Trump 'ISIS' Best Recruiter'
Clinton took several opportunities to take direct aim at Republican front-runner Donald Trump, at one point citing his rhetoric as a powerful and potent tool for the Islamic State.
"He is becoming ISIS's best recruiter," Clinton said. "They are going to people showing videos of Donald Trump insulting Islam and Muslims in order to recruit more radical jihadists."
Clinton provided no further evidence to back up her claim, and ABC News reached out to the Clinton campaign for comment.
In the wake of the ISIS-inspired mass killing in San Bernardino, Calif. earlier this month, Clinton also said she does not believe calls to arm more Americans -- an idea that Trump has pushed -- will make Americans safer.
"Guns, in and of themselves, in my opinion will not make Americans safer," she said. "We lose 33,000 people a year already to gun violence. Arming more people to do what I think is not the appropriate response to terrorism."
3. Sanders' Moment Of Zen
Sanders -- usually one of most animated orators in the 2016 field -- ended up being the one to tell one of his own rivals to "calm down."
"Whoa, whoa, whoa. Let's calm down a little bit, Martin," Sanders said during a discussion on O'Malley's record on gun control.
"It's because of the flip-flopping political approach of Washington that both of my two colleagues on the stage have represented for the last 40 years," O'Malley said before being interrupted by Sanders.
But Sanders had his own fiery moment later in the exchange.
"Please do not explain to me, coming from a state where Democratic governors and Republican governors have supported virtually no gun control," he said as O'Malley tried to interrupt. "Excuse me. Do not tell me that I have not shown courage in standing up to the gun people."
4. No-Fly, No Problem?
Clinton, the former Secretary of State, held firm when challenged by moderator Martha Raddatz on her promise to create a no-fly zone in Syria in order to stabilize certain parts of the war torn country.
When asked by Raddatz if she would shoot down a Syrian or Russian aircraft in order to enforce a no-fly zone, Clinton declined to elaborate.
"I do not think it would come to that. We are already deconflicting airspace," Clinton insisted, "I am advocating the no-fly zone both because I think it would help us on the ground to protect Syrians."
Sanders expressed concerns about the ability to enforce such a policy, saying it leaves certain aspects of the conflict uncertain: "I worry too much that Secretary Clinton is too much into regime change and a little bit too aggressive without knowing what the unintended consequences might be."
5. Sanders Gets Challenged To 'Join the Democrats'
When the topic turned to gun control, Clinton used the question as an opportunity to challenge Sanders' voting record.
"I would hope, Senator Sanders, that you would join the Democrats who are trying to close the Charleston loophole, that you would sponsor or co-sponsor legislation to remove the absolute immunity," Clinton said.
For his part, O'Malley took a shot at both candidates: "ISIL training videos are telling lone wolfs the easiest way to buy a combat assault weapon in America is at a gun show, and it's because of the flip-flopping political approach of Washington that both of my two colleagues on the stage have represented for the last 40 years.
6. Hillary Goes Missing -- Briefly
When the debate returned from a commercial break -- Clinton was nowhere to be seen.
"We want to turn to American jobs, wages, and raises in this country. And do we believe Secretary Clinton will be coming around the corner any minute," moderator David Muir said.
Seconds later, Clinton returned to the stage to applause -- and one word: "Sorry!" she chimed in.
7. Everybody Loves Hillary?
In a rather light moment in an otherwise contentious debate, Clinton offered a snappy response when reminded of an old Fortune magazine headline with her photo on the cover and the headline: "Business Loves Hillary!"
"I'm curious, eight years later, should corporate America love Hillary Clinton?" moderator David Muir asked.
"Everybody should!" Clinton volunteered.
8. Of 'Lust' and Libya
When pressed on her responsibility for the chaos currently gripping the nation of Libya, Clinton stopped short of saying mistakes were made during the U.S. intervention that ousted Libyan strongman Gaddafi.
"Well, there's always a retrospective to say what mistakes were made," Clinton said, "But I know that we offered a lot of help and I know it was difficult for the Libyans to accept help.
While both Sanders and O'Malley did not directly disagree with Clinton's role in the Libyan intervention, they questioned the motivations for U.S. action.
"I think Secretary Clinton and I have a fundamental disagreement. I'm not quite the fan of regime change that I believe she is," said Sanders.
"In this case we probably let our lust for regime toppling get ahead of the practical considerations for stability in that region," said O'Malley.
9. Presidential Spouses Take Center Stage
As the debate ended, the moderators asked all three candidates about the role their spouses might play if elected, including Clinton, who has played that role herself as a former First Lady during her husband's presidency.
"With respect to my own husband, I am probably still going to pick the flowers and the China for state dinners and stuff like that," Clinton acknowledged. "But I will certainly turn to him as prior presidents have for special missions, for advice, and in particular how we're going to get the economy working again for everybody, which he knows a little bit about."
Sanders called his wife, Jane, "a lot smarter" than him.
"I think we need a forceful advocate for the children, for teenagers, for the little children to deal with the dysfunctional childcare system," he said, "and I think my wife would do a great job in helping me accomplish those goals.
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Tensions boiled over gun control during Democratic Debate