Trump and Biden dominate Super Tuesday contests

President Joe Biden and former President Donald Trump swept to victory in statewide nominating contests across the US, setting up a historic rematch in November's general election despite low approval ratings for both candidates.

Trump won the Republican votes in a dozen states - including delegate-rich California and Texas - brushing aside former U.N. Ambassador Nikki Haley, his lone remaining rival, whose campaign no longer has a viable path to the nomination. Her only win of the night thus far came in Vermont, Edison Research projected.

After a commanding performance across 15 states where more than one-third of Republican delegates were up for grabs on Super Tuesday, Trump had all but clinched his third consecutive presidential nomination, despite facing a litany of criminal charges.

Trump and Biden trained their focus on each other as the results became clear. In a victory speech delivered at his Mar-A-Lago estate in Florida, Trump attacked Biden's immigration policies and called him the "worst president" in history.

"November 5th is going to go down as the single most important day in the history of our country," Trump said.

In a statement, Biden again cast Trump as a threat to American democracy.

"Tonight's results leave the American people with a clear choice: Are we going to keep moving forward or will we allow Donald Trump to drag us backwards into the chaos, division, and darkness that defined his term in office?" Biden said.

Biden had been expected to sail through the Democratic contests, though a protest vote in Minnesota organised by activists opposed to his forceful support of Israel attracted unexpectedly strong results.

The "uncommitted" vote in Minnesota stood at nearly 20 percent with more than half the estimated vote counted, according to Edison, higher even than the 13 percent that a similar effort in Michigan drew last week. Biden nevertheless won Minnesota and 14 other states, including a mail-in vote in Iowa that ended on Tuesday.

He did suffer one loss, in the U.S. territory of American Samoa's caucus, where entrepreneur Jason Palmer won 51 votes to Biden's 40, according to the American Samoa Democratic Party.