A former prosecutor, Harris, 59, appeared to get under the former president's skin with a series of sharp attacks, prompting a visibly angry Trump to deliver a stream of falsehood-filled retorts.

The Democratic vice president unveiled a list of policies on her website on the eve of the clash, with Republicans accusing her of "flip-flopping" on key issues.

US President Joe Biden is facing a brutal reckoning after he repeatedly stumbled during Thursday night’s debate, with some Democrats calling for him to step aside ahead of the November election.

Thursday's debate comes at a moment of profound polarization and deep-seated anxiety among voters about the state of American politics.

Both Ted Cruz and John Kasich have fallen by the wayside, while Donald Trump dashed to the finishing line of Republican Party nomination for the US presidential race in 2016.

Hillary Clinton and Bernie Sanders come to blows in a heated US presidential debate in Brooklyn, raising the stakes in their increasingly acrimonious race to clinch the Democratic nomination.