A resurgent Joe Biden rolled to victories across the South, Midwest and New England on the biggest day of voting in the US Democratic presidential nomination campaign, setting up a one-on-one battle against Bernie Sanders, who led in California.

Biden, the former vice- president whose campaign was on life support just weeks ago, won nine of 14 states voting on “Super Tuesday”, including surprise wins in Texas and Massachusetts, in the race to face President Donald Trump in November.

Just days after his campaign was resurrected by a thumping win in South Carolina, Biden, 77, emerged as a consensus champion for the moderate wing of the party against Sanders, 78, a left-wing senator with strong support among the youth.

“For those who have been knocked down, counted out, left behind, this is your campaign,” Biden told roaring supporters in Los Angeles. “We are very much alive!”

In what would be the day’s biggest upset, Biden was projected by Edison Research to have won Texas, the biggest prize after California. Sanders invested heavily in Texas and was counting on its Latino population to propel him to victory.

Sanders, the one-time front-runner who had hoped to take a big step towards the nomination on Tuesday, won Colorado, Utah and his home state of Vermont, Edison Research said.

Democratic presidential candidate former Vice President Joe Biden speaks, next to his wife Jill during a primary election night rally on Tuesday (AP)

Biden, with overwhelming support from African-American, moderate and older voters, swept to wins in Alabama, Arkansas, Massachusetts, Minnesota, North Carolina, Oklahoma, Tennessee and Virginia.

Fox News and AP projected Sanders won California, whose 415 delegates represent the largest haul.

Edison Research and other networks held off declaring a winner there as results trickled in.

Maine was a toss-up, with both Biden and Sanders winning roughly a third of the vote with 73 per cent of the precincts reporting.

Without naming him, Sanders took direct aim at Biden during a rally with supporters in Vermont, criticising his 2002 vote to authorise war in Iraq and his support for global trade deals that Sanders opposed.

“We’re going to win the Democratic nomination and we are going to defeat the most dangerous President in the history of this country,” Sanders said, referring to Trump.

Bloomberg ends run

Billionaire former New York Mayor Michael Bloomberg ended his presidential campaign on Wednesday and said he was backing Joe Biden for the Democratic Party’s nomination to challenge President Donald Trump in the November election.