In a rambling answer, the former vice president began to speak about his work to curb institutional segregation, but ended by talking about a record player, saying people should have it on at night so poor children can learn new words.
Sanders, who has been praised by Biden as being honest with the American people that their taxes would go up if the country moves to "Medicare for All", weighed in by citing the costs the country would bear if the nation does not move to Medicare for All.
The third Democratic debate seemed to end in a 10-way tie.
For the first time Thursday, frontrunner Joe Biden faced his two leading left-leaning competitors on the debate stage: Sen. It was a signal that the policy-focused strategy that has buoyed her presidential campaign is unlikely to change, and that she is betting she can let other candidates fight it out while she sells her ideas.
Sen. Cory Booker (D-NJ) closed out the discussion by saying "we can not sacrifice progress on the altar of purity". Elizabeth Warren was more in the background than in prior debates but didn't damage herself, and closed with a compelling personal story.
"President Trump, you have spent the last two-and-a-half years full time trying to sow hate and division among us, and that's why we've gotten nothing done", Harris declared. Former Texas Rep. Beto O'Rourke called him a white supremacist.
The previous debate on July 31 also was stopped when protestors shouted about the Eric Garner case during Cory Booker's opening statement.
Entrepreneur Andrew Yang made a proposal that sounded like paying doctors a flat rate per patient, though the specifics were unclear.
But during Thursday night's debate, it was former Housing and Urban Development Secretary Julian Castro who attempted to bash Biden-this time, seemingly hitting him on his age and memory.
The likely result: little change in a primary that has been remarkably static for months.
Certainly, the head-to-head confrontation will come if Biden continues as the front-runner and Warren maintains her momentum as perhaps the most likely progressive alternative.
Sanders took heavy fire on his single-payer health insurance proposal, with Biden and others hammering the Vermont senator for the cost and the political palatability of effectively eliminating the existing private insurance market. Sanders' argument is that most US households would pay less overall under his system, even if their taxes go up. "For a socialist, you have a lot more confidence in corporate America than I do".
Buttigieg piled on Sanders, too.
"This discussion has given the American people a headache", she said.
In the second tier are candidates who have had a moment in the spotlight, but since lost some luster.
"We can not ask our military to keep solving problems that can not be solved militarily", she said. Castro said to Biden. Castro asked. "I can't believe that you said two minutes ago that you have to buy in and now you're forgetting that".
"I know that the senator says she's for Bernie, I'm for Barack", Biden said.
"I think candidates have seen, not just in the debates, but over the course of this campaign, that attacking Joe Biden is not the way to advance yourself in the polls", Biden deputy campaign manager Kate Beddingfield said after the debate.