But even as they cheered the House impeachment inquiry and argued that Trump needed to be removed from office, most Democrats on the debate stage in Atlanta, Georgia, used the question about impeachment to pivot to their core campaign message.
As in past debates, the candidates also disagreed on Warren's proposal to raise taxes on the wealthy.
Biden's standing is also a barrier to other white candidates, including South Bend, Indiana, Mayor Pete Buttigieg, who is surging in overwhelmingly white Iowa but struggling badly with black voters in Southern states like SC that have proven critical to previous Democratic nominees. "They know who I am", said Biden.
"If I'm [Michael] Bloomberg and I'm watching, I say to myself you've got Biden doing pretty well, Pete [Buttigieg] doing pretty well". Within minutes of the start, Warren found herself on the defensive as she explained she still supports a single-payer government run insurance system - "Medicare for All" - despite her recent modified proposal to get there in phases.
As Wednesday's debate came to a close, Booker made a plea to voters.
"For too long candidates, I think, have taken for granted constituencies that have been the backbone of the Democratic Party", Harris said.
Before becoming president Donald Trump had less foreign policy experience than Buttigieg does today, and has never served in the U.S. Armed Forces - except for his title of Commander-in-Chief.
She also raised the issue of rewarding big donors with plum embassy postings during the Democrat's presidential debate on Wednesday. Booker went on to note that black voters are "pissed off" and that Democrats need to address the fact that marijuana criminalization of marijuana disproportionately harms people of color if they want a shot at beating President Trump in 2020.
But Wednesday night's encounter did underscore a crucial difference between two of the top candidates circling Iowa: As Buttigieg sought to command the stage with his rhetoric, speaking of a "tender moment" coming at the end of a Trump presidency or the overarching need to unify the nation, Warren dove into the details, using nearly every question posed to her as an opportunity to dig into one of her plans, and occasionally urging her opponents to agree with her. "I do have the experience of feeling like a stranger in my own country, turning on the news and seeing my own rights coming up for debate". Kamala Harris, a historical foe of Biden's in past debates shook her head and moved on.
Healthcare reform figured prominently in the four previous Democratic debates; the fifth debate was no exception. But, he continued, "I do think it makes sense, based on data, that we should study what the long-term effects are for the use of marijuana".
"Impeachment is taking up oxygen, and it's freezing in place the status of the top four", said Brian Fallon, who was a top advisor to Hillary Clinton's presidential campaign in 2016. While she was careful to say she believed Buttigieg is qualified, she reiterated her argument that women are held to a higher standard.
Gabbard dismissively replied that Harris' response "only makes me guess that she as president will continue the status quo". Buttigieg had no black support in the state.
Warren, who has been making a particular effort to connect with black women, said that her policies on housing and eliminating student debt would reduce discrimination against blacks.
"I come out of the black community in terms of my support", Biden said.