HOUSTON _ Joe Biden, Bernie Sanders and Elizabeth Warren entered Thursday's debate as the clear-cut front-runners in the Democratic presidential primary.
But it was the comparative afterthoughts struggling at the bottom of most polls _ including Amy Klobuchar, Cory Booker and Beto O'Rourke _ who made the biggest impressions in Houston.
These struggling candidates regularly produced the third Democratic debate's most memorable moments, directly attacking the leading contenders, making impassioned pleas for ending gun violence, and calling for unity in the fight against President Donald Trump.
Whether these moments last beyond Thursday night, however, remains to be seen. The Democrats outside of the top three in the 2020 race struggled to break through in a lasting way after the previous two debates.
But for White House hopefuls like Klobuchar and O'Rourke, whose candidacies have thus far underwhelmed, their performances will offer hope they can get their campaigns back on track before their support and money erode away completely.
Here are four other takeaways from Thursday night's debate:
BIDEN BASHING REDUX
Another debate, another night of harsh criticism for Biden _ but this time the attack came from an unexpected source.
Julian Castro appeared to question the former vice president's mental fitness nearly a half-hour into the debate, accusing Biden of reversing himself on a health care policy position he took just minutes earlier.
"Are you forgetting what you said two minutes ago?" Castro said, eliciting a loud reaction from the audience. "Are you forgetting already what you said just two minutes ago?"
Biden protested _ during the debate he said "if you lose the job from your insurance company, from your employer, you automatically can buy into" a public health care option _ but the exchange was among the most memorable of the night.
It was far from the only attack against Biden _ Sanders, for instance, criticized his past support of free trade agreements and initial support for the Iraq War. But for Biden, Castro's criticism was another fraught moment on the debate stage, more than two months after Kamala Harris criticized him for his opposition to federally mandated busing for school children.
Of course, Harris' criticism failed to dislodge Biden as a front-runner. Despite a litany of questions about his performance on the campaign trail, he leads in nearly every poll of the race. But questions about his verbal gaffes are already a delicate subject, and likely to receive a renewed focus now.
But Castro also incurred some backlash for his line of attack. Appearing on ABC after the debate, former Barack Obama chief of staff Rahm Emanuel called Castro's swipe "disqualifying."
HARRIS GOES ALL IN ON TRUMP ATTACKS
Heading into Thursday night, the political world wondered which Harris would show up in Houston. Saddled with stagnant single-digit polling numbers and anxious donors, the California senator could've chosen to try and remake her first debate, when her premeditated attack on Biden proved fruitful but fleeting. What she couldn't afford was a repeat of the second debate, when she looked unprepared to defend her own record.
In the third debate, Harris recalibrated with a finely tuned, albeit safer focus on Trump, in an attempt to present herself as a unifier. She was the lone candidate to deliver a direct-to-camera message to Trump during her opening statement. She accused him of "tweeting out the ammunition" for the El Paso shootings and in a memorable, pithy zinger compared him to the Wizard of Oz. "When you pull back the curtain, it's a really small dude," she said, chuckling at her own joke.
Even on her diciest turf of "Medicare for All," rather than embarking on a fight with her rivals, she doled out credit to both President Barack Obama and Sanders for moving the ball on health care, while explaining her own modified plan. She then declared the details around the issue were giving people a headache and returned to attacking Trump.
MODERATES STRIKE BACK ON HEALTH CARE
The more moderate Democratic candidates finally found their footing in the party's ongoing health care debate.
In the previous two debates, progressives like Warren and Sanders set the tone when the discussion turned to health care, advocating for a single-payer system while swatting away questions about its cost and political feasibility.
But things were different Thursday. A relative moderate like Klobuchar took the Sanders and Warren proposals head on, forcefully arguing they were unrealistic because they would push people off their private health care insurance.
"While Bernie wrote the bill, I read the bill," said the Minnesota senator, a twist on Sanders's frequent declaration that he wrote the single-payer legislation that's drawn support in the Senate. "And on page eight of the bill, it says we will no longer have private insurance as we know it.
"I don't think that's a bold idea," she added. "I think it's a bad idea."
Biden and Pete Buttigieg offered similar denunciations, declining to shy away from a fight over an issue of visceral importance to some progressives that centrist critics have derided as harmful in a general election. Instead of supporting a complete government takeover of the insurance market, candidates like Biden have instead supported allowing adults to buy into a government-backed insurance plan if they'd like, but keep their private health insurance if they prefer.
It was the third consecutive debate in which health care dominated a long chunk of the discussion. And it's an issue that will continue to be a major fault line in the primary.
O'ROURKE (FINALLY) FINDS HIS MOJO
A central hamstring of O'Rourke's campaign has been self-lament. He's apologized for jokes about his wife, for appearing on the cover of Vanity Fair, for benefiting from "white privilege." In making the connection between Trump's rhetoric and the country's ghastly spate of gun violence, the former congressman recently confided to New York Magazine he's "failed to meet this threat with the urgency it requires."
On Thursday night, he finally met a klieg light moment with lightning-bolt urgency.
"Hell yes, we're going to take away your AR-15, your AK-47," O'Rourke said, generating the loudest applause line of the three-hour debate and bringing some attendees to their feet. "We're not going to allow it to be used against a fellow American anymore."
It was as if all the passion that O'Rourke has plowed into his personal campaign against gun violence over the last month and a half had finally summoned a clear-cut courageous voice that many Democrats were craving.
Even O'Rourke's opponents took time to heap praise on his all-consuming response to the August shooting in his hometown. As Jay Inslee found, single-issue campaigns are risky, but O'Rourke's moment gave him his best opportunity to break out of the polling basement.
