21:30

Guardian political correspondent, Lauren Gambino, writes that tonight’s debate will see Joe Biden face rival Kamala Harris in a highly anticipated rematch after a searing confrontation during last month’s presidential debate.

The former vice-president has also traded jabs with Bernie Sanders and Harris over healthcare, which was a major topic of debate on Tuesday night and revealed some of the sharpest divisions in the party.

Harris released her version of a Medicare for All plan that would cover all Americans without abolishing private health insurance. But the California senator is likely to face questions over how she would implement such a plan without raising taxes on middle-class Americans, as she has insisted is possible.

Biden, who has released a healthcare plan that would build on the Affordable Care Act passed under the Obama-Biden administration, said Harris’s claim that it is possible to pay for Medicare for All without raising taxes on the middle class existed in “a fantasy world”.

No candidate mentioned Biden on Tuesday, in a sign that despite his early lead in the primary contest, his campaign – or at least his ideas – is not dominating the field.