Here's a quick rundown of what happened:
* There was no clear winner, so to say — Sanders hit Clinton hard on her taking speaking fees from big banks. Clinton went after Sanders on his policies, saying they were "just not achievable."
* There was an ongoing battle over who the true "progressive" was and who was capable of "progress." The words were used so much, we kept count.
* The candidates also hit on the death penalty; the Flint, Michigan water crisis; and which nation poses the greatest threat to the U.S.
* The debate came three days after the Iowa caucuses, the first nominating contest of the season, where Clinton won by a very slim margin. The New Hampshire primary is Tuesday, and Sanders holds a big lead in the polls.
* Also, Sanders made a bunch of funny faces and Clinton brought her good luck charm. More on those below.
Clinton came out swinging, saying some of Sanders' proposals are "just not achievable."
"Senator Sanders and I have some very big, progressive goals," Clinton said.
"Republicans want to repeal the Affordable Care Act, I want to improve it. Sanders wants us to start all over, I am not going to wait and have this plunge back into a contentious national debate that has very little change of succeeding," she said.
"I also believe in affordable college, but I don't believe in free college."
"I want to make sure middle class kids, not Donald Trump's kids, can afford to go to college."
"The numbers just don't add up from what Senator Sanders has been proposing...it is just not achievable," Clinton said.
Sanders retorted, "The idea that I will dismantle healthcare in America...is just not accurate."
Both candidates argued — a lot — over who the real progressive is. (We kept count.)
As BuzzFeed News reporters Ruby Cramer and Evan McMorris-Santoro put it:
The great "who's the true progressive" debate continued Thursday night ahead of the New Hampshire primary here as Bernie Sanders and Hillary Clinton argued over the definition of progressivism, talking semantics and tearing down one another as less than pure lefties.
This, in a surprising turn, wasn't bad news for Clinton.
For the first time in an eight-month race, she was able to really puncture the attack from Sanders, a Democratic socialist, on the topic of liberal purity. Sanders and his supporters have used the Vermont senator's ideological message and combative voting record in Congress to suggest he's the candidate who can't be bought or moved to the middle.
Read more here.
After Sanders said that he believed Clinton “represents the establishment,” while he represents “ordinary Americans,” Clinton chuckled.
"I've got to just jump in here," she began with a smile, "because honestly Senator Sanders is the only person who I think would characterize me, a woman running to be the first woman president as exemplifying the establishment."
Sanders responded with a comment about connections to large corporations, adding that he took no money from corporations at any point in his career — implying Clinton has, in political donations and speaking fees.
Clinton quickly interrupted, calling the statement, and statements like it that Sanders has made throughout his campaign, "Innuendo and insinuation," implying anyone who takes money from interest groups is taking bribes. "I think it's time for your campaign to end a very artful smear and for us to talk about the issues."
Here are the two key clips of that exchange:
Sanders, decrying the lack of prosecution of Wall Street bankers after the 2008 financial collapse, drew a strong comparison between the punishment of drug offenders and bank executives.
In case you need more clarity on Sanders' position on big banks, watch this:
And now, the ~lightning round~:
On the death penalty:
— Clinton said she wished the Supreme Court would ban state-sanctioned executions if the state cannot uphold "the highest standards of evidentiary proof" and reserve the death penalty for federal offenders, "for heinous crimes like terrorism."
— Sanders is against it. He said "too many innocent people, including minorities" are being executed even though they were innocent. "In a world of so much violence and killing," he added, "I just don't believe that government itself should be part of the killing."
On the Des Moines Register calling for an Iowa caucus vote recount (Clinton beat Sanders by about .3%):
— Sanders said that the Iowa caucuses were "chaotic," and took "half a dozen coin flips." Though he said he believed there needs to be a change in how votes are counted, he thought the delegates will "break relatively even."
— Clinton smiled and said, "Whatever they decide to do, that's fine."
On what order they would place Russia, North Korea, and Iran according to U.S. threat level:
— Both Clinton and Sanders put Iran last.
— Sanders said he believed North Korea was the most threatening of the three countries. "North Korea is a very, very strange country because it is so isolated and paranoid," Sanders said, adding that their nuclear capabilities are only increasing.
— Clinton said Russia was far more concerning due to the "pressure [Putin] is putting on our European allies."
Moderators then asked Clinton about her taking money from Wall Street in speaking fees after she was Secretary of State. She said she could have explained what she was doing better to voters:
"I may not have done the job I should have in explaining my record," Clinton said. "I did go on the speaking circuit...I spoke to heart doctors...auto dealers."
She went on, "I went to Wall Street before the crash. I was the one saying, 'You're going to wreck the economy.'"
She said she called for CEO compensation changes and consumer protections. Wall Street, she said, "is trying to beat me in this primary."
But when asked by moderators if Clinton would release full transcripts of her speeches to the bankers, she said, "I'll look into it, I don't know the status."
Back to business. Asked if she could assure Democratic voters that the investigation into her emails wouldn’t “blow up her candidacy” in the general election, Clinton said, “Absolutely, I can.”
Clinton compared the controversy over her emails to questions about her handling of the Benghazi attacks, accusing members inside the government of leaking information to hurt her politically.
"I agree with completely with Secretary Powell, who said today, 'This is an absurdity,' and so I think the American people will know it's an absurdity, " Clinton said, railing against what she called the over-classification of information contained in her emails. "I have absolutely no concerns about it whatsoever."
Pressed if she was 100% confident that nothing would come from the FBI investigation, she said, "I am 100% confident. This is a security review that was requested. It is being carried out. It will be resolved. But I have to add, if there's going to be a security review about me, there's going to have to be security reviews about a lot of other people, including Republican office-holders because we got this absurd situation of retroactive classification. Honest to goodness. This is — this just beggars the imagination."
It wasn't all snippy — both declined to attack each other at several points. Sanders refused to engage on a Clinton email question, and Clinton has this one-word answer when asked about Sanders staffers allegedly caught impersonating union workers:
Here's another moment of peace:
And we'll end on this: When a reporter pointed out that Clinton has worn the necklace her husband, Bill, got for their last anniversary at every debate, BuzzFeed News reporter Ruby Cramer said she's learned it's a good luck charm.
Here more coverage of the debate:
Read more coverage of the Democratic campaign:
Reporting by Ema O'Connor, Kyle Blaine, Tom Namako, Ruby Cramer, and Evan McMorris-Santoro.