Each candidate had at least eight minutes of speaking time tonight — and every one had at least one standout one-liner, compelling argument or tense exchange.
Here's a look at the candidate's most dramatic, most humorous and most riveting moments.
Sen. Michael Bennet mentioned his mother, an immigrant who was separated from her parents during the Holocaust in Poland, and said she's part of the reason immigration is an issue that's important to him:
"For those reasons, I was part of the gang of eight that wrote — I wrote the immigration bill in 2013 with John McCain that passed the Senate with 68 votes that gave a pathway to citizenship for the 11 million undocumented people that are here," he said.
Sen. Kirsten Gillibrand directly questioned former Vice President Joe Biden about an op-ed he wrote on about women working outside the home. She repeatedly asked him what he meant when he wrote that working women would "create the deterioration of family." Even as Biden defended why he voted against a child care funding bill, she kept pressing him on the op-ed:
"Mr. Vice President, I respect you deeply. I respect you deeply. But those words are very specific. You said women working outside the home lead to the deterioration of family."
Julián Castro, the former secretary of Housing and Urban Development, criticized Biden's position on border crossings after the former vice president said that illegally crossing the border should remain a crime. Castro responded:
"It looks like one of us has learned from the lessons of the past and one of us hasn't."
Sen. Cory Booker got into a heated exchanged with Biden over criminal justice reform and criticized him with this line:
"There's a saying in my community that you're dipping into the Kool-Aid and you don't even know the flavor."
Sen. Kamala Harris spent her debate night aggressively attacking Biden. The very first question of the night became an opportunity for the two to debate on their dueling heath care plans. Later, she called out the former vice president out for changing his position on abortion funding.
Former Vice President Joe Biden spent the majority of the night defending himself against attacks from the other candidates. He got into it with Harris over his changing position on a measure that blocks federal funds from being used for most abortions. Biden also struggled to answer Democratic foes who criticized Obama-era deportations of undocumented immigrants. In a separate moment, protesters began chanting in the debate hall after Biden was asked about deportations under the Obama administration.
Businessman Andrew Yang offered this fiery comparison between himself and Trump in his opening remarks:
"We need to do the opposite of much of what we're doing right now and the opposite of Donald Trump is an Asian man who likes math."
Later on, he defended immigrants, saying they're "being scapegoated for issues they have nothing to do with in our economy."
Hawaii Rep. Tulsi Gabbard, the only war veteran on stage tonight, said most policymakers in Washington can’t fathom the cost of the war. Her political record has come under intense scrutiny over the past few years, but Gabbard’s criticism of the US foreign policy establishment is in line with most progressives’ — and she pulled no punches on stage tonight.
Washington Gov. Jay Inslee challenged Biden on the urgency of climate change. He then a passionate defense for action on climate changing, saying:
"We cannot work this out. The time is up. Our house is on fire. We have to stop using coal in 10 years and we need a president to do it or it won't get done. Get off coal. Save this country and the planet."
Mayor Bill de Blasio came under fire tonight for not taking action against New York City police officer, Daniel Pantaleo, who choked Eric Garner to death. Protesters disrupted the debate demanding Pantaleo's firing. Several candidates also called on the mayor to fire the officer.