DEMOCRATIC presidential hopeful Bernie Sanders received a major boost as a new poll showed him jointly leading the race to take on US President Donald Trump in the 2020 elections.

The data from Monmouth University published on Monday put Mr Sanders on 20 per cent — up six points since the last poll in June. He was level with Elizabeth Warren, who gained five points and is also polling at 20 per cent of the national vote.

The biggest loser was former vice-president Joe Biden, who dropped 13 points, slumping to third place on 19 points.

Monmouth polling institute director Patrick Murray said: “The main takeaway from this poll is that the Democratic race has become volatile.

“Liberal voters are starting to cast about for a candidate they can identify with. Moderate voters, who have been paying less attention, seem to be expressing doubts about Biden.”

Mr Biden’s supporters pointed to last week’s CNN poll which showed he had a 14-point lead over Mr Sanders. But others have noted an “enthusiasm challenge” for voters regarding the former VP, who has regularly faltered in stump speeches during his third presidential campaign.

The primaries will take place from February to June 2020.