The early portion of Thursday's debate exposed the ideological fault lines in the Democratic field. Biden pitched his candidacy as building on the legacy of former President Barack Obama, while the Senators from Massachusetts and Vermont advocated for fundamental changes to the American economy and federal government, reports Efe news.
Biden also sought to paint his candidacy in transformational terms, invoking late President John F. Kennedy as he called for investing in cures for cancer and other diseases.
"We're the best-equipped nation in the world to take this on. It's no longer time to postpone. We should get moving. There's enormous, enormous opportunities once we get rid of Donald Trump," Biden said.
Warren also paid homage to Obama, praising him for passing the Affordable Care Act.
"We all owe a huge debt to President Obama, who fundamentally transformed health care in America and committed this country to health care for every human being," Warren said, adding that the goal now should be to improve upon Obamacare.
Biden, Warren and Sanders were joined on stage by the other seven top polling candidates, another first in the primary debates.
The debate, hosted by the ABC Network in Houston, saw health care bringing out the largest disagreement among the candidates.
Sanders took broadsides over his Medicare-for-All plan. The proposal, which Warren has endorsed, would move every American onto a government-run health insurance plan regardless of whether they have insurance through their employer.
Biden and more moderate candidates, like Senator Amy Klobuchar of Minnesota and South Bend (IN) Mayor Pete Buttigieg, criticized the plan as going too far.
"I think Obamacare worked," Biden said, as he cast Sanders's proposal as taking too long to implement while many Americans don't have health care currently. Biden has favored a public-option approach in which a government-operated program would compete with private insurers.
Biden also aggressively went after Sanders and Warren over their calls to increase taxes to pay for their ambitious health care proposal.
"It's not a bad idea if you like it; I don't like it," Biden said.
But Biden drew his criticism from Sanders and former Housing and Urban Development Secretary Julian Castro, who said his plan is too incremental and not providing broad enough coverage.
"I'm fulfilling the legacy of Barack Obama and you're not," Castro told Biden.
Early in the debate, former Texas Repreentative Beto O'Rourke used the spotlight to talk about the shooting in his hometown of El Paso, where 22 people were killed at a Walmart shopping centre.
He accused Trump of welcoming racism and violence into the country and criticized the current political landscape as insufficient to meet the growing threat of violence.
"The bitterness, the pettiness, the smallness of the moment, the incentives to attack one another and try to make differences without distinctions, mountains out of mole hills, we have to be bigger," O'Rourke said
California Senator Kamala Harris took a jab at Trump in her opening statement. "You have used hate, intimidation, fear and over 12,000 lies as a way to distract from your failed policies and your broken promises," she said.
Entrepreneur Andrew Yang sought to draw attention early on in the debate by announcing that his campaign will randomly select 10 people to receive $1,000 a month for a year, a trial run of his signature campaign proposal to provide families with payments of $12,000 a year.
The raffle drew some laughter in the audience and from Buttigieg, who quipped: "It's original. I'll give you that."
Only 10 other Democrats remain in the race, but just one - former hedge-fund manager Tom Steyer - has met the polling and fundraising requirements to qualify for the next debate in October.