Unsurprisingly, the coronavirus pandemic - and the candidates' plans for addressing it - dominated the debate.
Just before the Democratic debate Sunday, the Centers for Disease Control and Prevention put out guidelines encouraging Americans not to gather in groups of 50 or more for the next eight weeks. He also said that people who enter the US illegally will not be deported unless they commit a felony on American soil, even if they have a criminal record in another country.
Here's a look at some of the other the key moments and conflicts. Bernie Sanders have taken the stage for the first one-on-one debate of the Democratic primary.
"There are a number of women who are qualified to be vice president tomorrow", Biden added. Sanders hegded a bit, saying that "in all likelihood" he would, too, but wanted a "progressive woman".
The opening 30 minutes, about how to address the coronavirus outbreak, captured the two candidates' messages well. Biden said he wanted to re-enter the Paris Climate Accords, ban offshore drilling, and limit any new fracking.
Biden, the frontrunner, recounted his experience as serving in President Barack Obama's administration in dealing with the Ebola outbreak in 2014. Pass the Biden healthcare plan, which takes Obamacare, restores all the cuts made to it, subsidizes further, provides for lower drug prices, makes sure that there's no hidden bills, makes sure that we invest what I want to invest, $50 billion in dealing with underlying diseases that are of great outcome - diabetes, Alzheimer's and cancer - makes sure that we have a Medicare option that's in a public option providing Medicare for us.
Biden is widely expected to add to his delegate lead over Sanders when votes are cast in Florida, Ohio, Illinois and Arizona. For political gain, he also unhelpfully decoupled the foundational problems of our immiserating healthcare system from the current struggle to handle an outbreak, noting that Italy has a single-payer system and it's not helping them.
Nation writer (and former Salon editor) Joan Walsh responded to Sanders by saying, "it's nice he's giving Biden a takehome exam for the debate on Sunday".
Gunman kills 4, injures 2, then 'shoots self' in US
Investigators believe the gunman, who has not yet been identified, was responsible for all four shooting calls, Williams said. Walsh was with the Springfield police for three and a half years, was an army veteran and was active in the army reserves.
Is there any point in trying to appease Sanders?
Sanders draws blood Social Security The most heated section of the argument came after Sanders tore into Biden to get a litany of previous places - his stance about the 2005 bankruptcy legislation (that Biden has consented to unwind), his vote to authorize the Iraq war, his support to the Defense of Marriage Act from the'90s.
"You are an honest man". If you love Bernie Sanders, this is what you love about him: his absolute refusal to pander, ever. He also said the U.S. should "protect" the wages of Americans who lose their job because of economic damage from the crisis. His campaign staff has been working from home and Sanders also noted that, "I'm not shaking hands".
Biden said people want "results, not a revolution", are how we solve the economic crisis.
Democratic White House hopeful Joe Biden said during the presidential debate that he would "appoint a woman to be vice president" if he is elected president. "But we don't disagree on the principle".
Both Biden and Sanders have had to cancel planned rallies, and on Sunday they acknowledged shifting from live rallies to televised or online events - and that they are both taking precautions to avoid getting infected.
In response, Sanders, who voted against the bank bailouts in the 2008 crisis, took the opportunity to discuss inequalities in income and distributions of wealth.
"All that I would say to the American people, go to the YouTube", Sanders said.
Last Tuesday's election results confirmed what most observers strongly suspected after the Super Tuesday returns a week earlier: Joe Biden will be the Democratic nominee for president in 2020.
It remains to be seen how well the former vice president, who is a prolific gaffe generator and sometimes seems to fade late in debates, will endure the two-hour encounter with Sanders.