Elsewhere during the two-hour debate, the other candidates attempted to introduce themselves to the millions of Americans watching along on television – many of whom will be unfamiliar with their policy stances.
The other six candidates present were US senators Kirsten Gillibrand and Michael Bennet, South Bend mayor Pete Buttigieg, former Colorado governor John Hickenlooper, entrepreneur Andrew Yang and author Marianne Williamson.
Healthcare proved one issue that split the field. Some candidates like Mr Sanders backed replacing all private health insurance with a public option while others – such as Mr Biden – supported more incremental change, building on Barack Obama’s flagship ‘Obamacare’ legislation.
When candidates were asked by moderators at NBC, the TV broadcaster hosting the event, whether their healthcare plan would cover undocumented migrants all 10 politicians raised their hand.
It led Mr Trump to tweet: “All Democrats just raised their hands for giving millions of illegal aliens unlimited healthcare. How about taking care of American Citizens first!? That’s the end of that race!”