Vermont Senator Bernie Sanders has won Utah, claiming victory in his third primary contest of Super Tuesday as polls close on the West Coast and early results emerge.

The state holds 29 delegates.

Utah's Democratic Party estimates Latinos represent 14 per cent of a state that is largely white, as the Vermont Senator's campaign has bet on its support among Latino and Hispanic communities to carry him to wins in crucial states.

In 2016, four in five Democrats chose Mr Sanders over Hillary Clinton, and he was projected to win 28 per cent of the vote in 2020 in a more-crowded field but wasn't guaranteed a landslide victory.

It was another state that held a caucus rather than a primary, much like Minnesota, which Mr Sanders also won.

Many voters mailed in their ballots in the days and weeks ahead of Tuesday, with a significant number of ballots counting towards candidates no longer in the race.

Moments before the race was called for the senator, he addressed a crowd in Vermont, taking aim at Joe Biden, who is carrying more state victories on Super Tuesday.

"You cannot beat Trump with the same ol', same ol' kind of politics", Mr Sanders said. "What we need a is a new politics that brings working class people into our political movement, that brings young people into our political movement, and in November will create the highest voter turnout in American political history."

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He said the race between him and the former vice president is a "contrast in ideas" between a senator who opposed the Iraq War ("you're looking at him") and another who voted for it, as well as opposing views on cutting Social Security and other issues on which both men are in stark contrast.

Mr Biden has won several states tonight, cementing his lead in the South, as Sanders pursues major victories in delegate-heavy Texas and California, which are the primary's bigger trophies, with a smattering of smaller states with fewer delegates to divvy among them.