On the other end, Joe Biden couldn’t have looked less like a frontrunner. His answer on age was effective, and he avoided a prolonged exchange focused on his son’s unseemly, foreign employment situations. But his lack of energy over three hours didn’t back it up. That he ended the third fundraising quarter with less money on hand than Sanders, Warren, Buttigieg and Harris is yet another concern for his seemingly plateauing campaign.

Adam Cancryn, health care reporter: The knives finally came out for Elizabeth Warren, and she ably parried them away across all three hours of the debate. Warren demonstrated she can handle the pressure that comes with being the frontrunner, even if it wasn’t always comfortable or particularly easy. And she did take some hits: from Buttigieg on Medicare for All, Andrew Yang on workforce automation and Klobuchar on nearly everything, all of which could open up fresh lines of attack down the road. But on Tuesday, Warren managed to minimize her weaknesses and turn those criticisms more often than not into opportunities to promote her range of policy platforms.

Putting 12 candidates on one stage means some are bound to get lost in the fray, and that was certainly the case for fringe candidates like Julián Castro and Tom Steyer. Both Castro and Steyer had some solid moments, particularly on impeachment and gun control. But they simply didn’t command the stage for long enough — and notably enough — to make much of a dent in a debate that centered largely on the established 2020 frontrunners.

Natasha Korecki, national political correspondent: Amy Klobuchar broke out in a way that she hasn’t in past debates and at a time when more centrist Democrats are perhaps considering an alternative to Joe Biden. This could have been a big night for Biden, between Syria and Trump’s recent attacks, but he just couldn’t execute.

But Elizabeth Warren moved into clear frontrunner status, as evidenced by the attacks on her all night. She dominated talking time and framed her answers in the kind of clear manner that Biden could not when the knives were out for him in earlier debates.

David Siders, national political correspondent: Elizabeth Warren won this debate, Joe Biden lost it — and it wasn’t even close. Yes, Warren once again ducked questions about whether her “Medicare for All” proposal would require a tax increase on Americans. But she’s been dodging that question forever, to no noticeable effect. The difference on Tuesday was that nearly every other candidate was targeting Warren — on issues ranging from health care to whether President Donald Trump should keep his Twitter account. The effect was to keep Warren firmly at the center of the stage, giving her time to counter every attack. And Warren is a skilled debater, turning issue after issue to her critique of money in politics and inequality in the United States.

Biden didn’t falter because he performed exceedingly poorly. He turned in a middling debate. But for the first time, expectations were higher for him Tuesday, with the Ukraine controversy and Warren crowding him at the top of public opinion polls. For a candidate who rests his entire candidacy on his ability to confront Trump, his answer on impeachment fell flat.

Daniel Strauss, campaign reporter: Sen. Elizabeth Warren had a good night because this debate showed that other candidates regard her as the one they have to knock down. Warren’s rivals were more eager to attack her than Biden, a clear sign they view her as the more important target.

It was a bad night for Tulsi Gabbard. After failing to qualify for the last debate, her return to the stage may be short-lived. She’s not assured a spot in the next debate — and did little Tuesday to change broaden her appeal.

Nahal Toosi, foreign affairs correspondent: I thought Pete Buttigieg had a strong night. His criticism of President Donald Trump’s decision to withdraw U.S. troops from northeast Syria seemed genuinely heartfelt and even indignant. He seemed passionate, not canned as he sometimes does on other topics.

On that same front, I’d say the weakest candidates were the ones who got less time on the air, like Beto O’Rourke and Julian Castro. They simply couldn’t stand out. One exception to that: Tom Steyer. In the short amount of time he had, the billionaire making his debate debut made sure to mention climate change as a national security issue, a message not heard often enough.

What surprised you?

Christopher Cadelago: Klobuchar was at her best when she challenged her opponents on the left, something that has tripped up her and others in the first three debates. Sanders bounced back after a heart attack, again taking it to Biden over his support for the Iraq War. The pending endorsement of Alexandria Ocasio-Cortez ended a serviceable return for Sanders — who, for whatever you might think about him, is the most authentic figure in the field.

Adam Cancryn: Klobuchar came out with a looseness and passion we haven’t yet seen from her — or really any moderate Democrat during the debates, save for Buttigieg. She made the kind of positive case for pragmatism that’s been in short supply this primary, while showing she’s not afraid to challenge the soaring ambitions of Warren and Sanders on both politics and policy.

Natasha Korecki: Buttigieg’s face off with O’Rourke — not because of the clash but Buttigieg’s seemingly deeply personal exchange with the Texas congressman. “I don't need lessons from you on courage, political or personal,” Buttigieg sniped at the Texan. It’s perhaps a testament to Buttigieg still feeling the need to draw a distinction with O’Rourke.

David Siders: Klobuchar, after drifting through three debates as a relative non-factor, in one night became a credible alternative to Joe Biden in the moderate lane. Her criticism of Warren on Medicare for All was some of the sharpest offered, and she landed one of the more memorable, off-the-cuff lines of the debate when she gave Warren what she called a “reality check.” She said, “No one on this stage wants to protect billionaires. Not even the billionaire wants to protect billionaires.”

Daniel Strauss: I was surprised that Buttigieg decided to engage with Gabbard, the only other veteran on stage. Her base in the primary is small, and her supporters are not likely to cross over to him. But he decided to get into a heated exchange with her on Syria and the Middle East anyway.

Nahal Toosi: I was surprised that Warren did not specifically name Biden at all in crediting former President Barack Obama and others for supporting the creation of the Consumer Financial Protection Bureau. He pointed out that he helped get votes for it, and she blew him off in a way that I think some people will see as lacking in grace.

Did we learn anything new?

Christopher Cadelago: Tom Steyer has spent more than a decade practicing for his moment, since plunging into politics in California. For a first-time debater, and with all the necessary caveats, Steyer managed to hold his own. “There have been 40 years where corporations have bought this government, and those 40 years have meant a 40-year attack on the rights of working people and specifically on organized labor,” Steyer said in his most memorable exchange, where he agreed with Sanders, the candidate who doesn’t think billionaires should exist. “It’s absolutely wrong. It’s absolutely undemocratic and unfair,” Steyer added, pointing to his early floating of a wealth tax.

Adam Cancryn: Four debates in, a handful of candidates are ready to stop being polite and start getting real. Warren, Buttigieg and Klobuchar all showed a willingness to throw particularly sharp elbows when challenged, even as Democrats more broadly are pleading for the field to keep focused on defeating Trump. While there was plenty of Trump-bashing during the debate, Warren showed little willingness to entertain criticisms of her policy prescriptions. And Buttigieg and Klobuchar made firm cases for joining Biden as standard bearers for Democrats’ moderate wing.

Natasha Korecki: We saw how Warren took her punches; there were a lot of them tonight and many were coming from the right: Klobuchar and Buttigieg. She’s going to get more questions on her plans, whether she can pay for them and if they’re too pie-in-the-sky. But in the end she stood her ground while Biden faded.

David Siders: Sanders is here to stay. This isn’t startling, given his strong fundraising and relatively firm base of support. But it’s possible that he is now a better candidate than he was before his heart attack. No gravelly voice tonight, as there was in the September debate. And he appears ready for a fight, as when he told Biden, “Joe, you talked about working with Republicans and getting things done. But you know what you also got done? And I say this as a good friend: You got the disastrous war in Iraq done.”

Daniel Strauss: We learned that Sanders does indeed seem fine after his recent heart attack. He was back to his usual self, and now the oldest candidate in the field can pitch himself as the comeback kid.

Nahal Toosi: Cory Booker is a vegan. (I’m kidding.) I can’t say on the foreign affairs front that I learned much new. Despite the leftist views of some candidates, such as Sanders, at the end of the day, there’s a lot of unanimity on the basic idea that the U.S. needs to have a presence on the global stage, maintain alliances and project consistency in its foreign policy. Easier said than done, I know.

How did the moderators do?

Christopher Cadelago: The moderators mostly kept things moving. And, unlike in past debates, the questions setting up confrontations between candidates elicited some sharp contrasts. The final question off of Ellen DeGeneres and George W. Bush’s unlikely friendship, however, evoked some of the most blatantly inauthentic and cringey politicking of the night.

Adam Cancryn: The moderators will undoubtedly — and somewhat deservedly — take some flak from the left for asking questions that parroted Republican attacks on Medicare for All as too costly, liberal jobs programs as unrealistic and the concept of a wealth tax as demonizing the rich. But overall, they did a competent job managing the discussion and should get major credit for hitting subjects like abortion rights and the Supreme Court that had gone totally ignored in prior debates.

Natasha Korecki: The moderators handled the age question tastefully, and that’s no easy task. They could have reined in candidate answers and kept them on task, especially early on when candidates at times shifted and talked about what they wished.

David Siders: The moderators controlled the conversation and hit a range of issues that lots of viewers will be happy with. But there was one missed opportunity: When questioning Warren about whether her Medicare for All proposal would require a tax increase, she ducked. The moderators followed up, checking the responsible moderator box. But given Warren’s elevated standing in the race, this is one question where they could have kept going back to it to force the point.

Daniel Strauss: They were fine until the very end with that unlikely friend question. There was nothing useful viewers could learn from that question. It was just a chance for each candidate to filibuster for a little bit.

Nahal Toosi: The moderators kept things under control for the most part, and they moved from subject to subject fairly efficiently. The decision to eliminate opening statements struck me as wise, and it was nice to see so many topics covered, though foreign policy deserved more time. Honestly, I was pretty impressed. (And I liked the last question about uncommon friendships. It made the candidates seem human.)

Who had the most cringe-worthy moment?

Christopher Cadelago: Harris’ pressing of Warren over suspending Trump’s Twitter account may be the stuff of successful cable news segments — and, hell, a lot of Democrats likely agree with her given the violence he’s incited. But it looked comparatively trivial on a presidential debate stage. Warren’s refusal to agree magnified the awkwardness. Booker’s “West Wing”-inspired soliloquy came off as tone deaf given the era and the stakes.

Adam Cancryn: Booker and Gabbard trying to jump in on the inevitable “age” question came off as completely contrived and was painful to watch in real time. Biden, meanwhile, struggled at times to come up with answers to Supreme Court-related questions that didn’t name-check Robert Bork — a failed Supreme Court nominee from more than 30 years ago who likely isn’t going to register with a wide swath of the electorate.

Natasha Korecki: The heated exchange between Biden and Warren over Warren’s push to create the Consumer Financial Protection Bureau had more than one awkward moment. First, Warren’s response to Biden interjecting that she did a good job of doing her job; she calmly thanked him. But it was equally awkward when Warren very obviously dissed Biden when she personally thanked Obama and purposely refrained from praising the former vice president who had just said he fought for votes for her. There’s likely more of a story there, but it isn’t clear that most viewers would get that.

David Siders: Booker sounded all night as though he had a bag of one-liners he needed to empty. His assertion of his qualifications as “the vegan” on stage to assess Trump’s health — “the most unhealthy person running” for president — was probably the pinnacle.

Daniel Strauss: Harris and Gabbard, separately, pressed Elizabeth Warren to say something, and Warren didn’t take the bait either time. Did they actually think she would? The result both times was just a lot of crosstalk.

Nahal Toosi: Gabbard kept using the phrase “regime-change wars.” I understand what she’s trying to get at — the idea that the U.S. shouldn’t engage in overthrowing other governments — but the phrase is clunky and awkward. And when she says a phrase like that in the context of questions about Syria, it’s misleading. U.S. troops in Syria have been fighting the Islamic State terrorist group, not the regime of Bashar Assad.

How will this change the trajectory of the race?

Christopher Cadelago: Several candidates have now established and broken the seal on lines of attack against Warren. Given her steady ascent, you can expect to hear a lot more of these types of attacks in the coming weeks as she faces the stress test of a frontrunner.

Adam Cancryn: Warren is now the clear frontrunner — and the prime target for the rest of the field. She faced tough questions about her range of policy proposals, and those attacks are only likely to increase as Buttigieg, Klobuchar and other moderate candidates try to gain traction. Biden, meanwhile, faces yet another stretch where he’ll need to prove he’s not just the best Democrat to take on Trump, but the best Democrat to lead the nation beyond the era of Trump.

Natasha Korecki: Biden faded tonight as Warren stepped into the limelight. We got a glimpse into the future: It won’t necessarily be an easy ride for Warren. Two aggressive and articulate candidates — Buttigieg and Klobuchar — are around to fact-check Warren and ask her to show her work.

David Siders: For candidates outside of the top three, Warren is now the candidate to smack — not necessarily to draw support away from Warren, but to position her as a foil. The real play for moderates is still to hope that Biden collapses. What the debate showed is that if he does, the path to winning over his supporters runs right through a sharp critique of Warren and the liberal left.

Daniel Strauss: Warren’s exchange with Biden on the creation of the Consumer Financial Protection Bureau could provide a window into how other Democrats can navigate Biden’s role in the Obama administration.

Nahal Toosi: If this debate, and the run up to it, have been any indication, Warren is now the frontrunner, and Joe Biden is fading. He didn’t really reverse that perception Tuesday night.