WASHINGTON - Donald Trump marched Wednesday towards an unprecedented rematch against President Joe Biden in November as his final Republican rival Nikki Haley looked set to throw in the towel after a thumping defeat in the "Super Tuesday" primaries.

Former UN ambassador Haley was to suspend her campaign shortly, and without endorsing Trump, US media reported.

This will leave America almost inevitably facing a bitter battle for the White House that many voters say they don't want, with Trump brushing aside multiple criminal indictments and the scandal over his attempt to overthrow the 2020 election in pursuit of a return to the world's most powerful office.

The 52-year-old Haley, who sought a path to victory by portraying her one-time boss Trump as chaotic and mentally incompetent, was expected to make her announcement in Charleston in her home state of South Carolina at 10:00 am (1500 GMT).

Former president Trump, 77, swept 14 out of 15 states up for grabs on the biggest day of the 2024 race so far, with Haley denying him only in the northeastern state of Vermont as he covets a second term in the Oval Office.

A voter casts their votes at a polling station in Nashville, Tennessee on Super Tuesday, March 5, 2024

Biden meanwhile swept the Democratic "Super Tuesday" primaries and will now gear up for Thursday’s State of the Union address, a defining moment as the unpopular 81-year-old seeks to allay voter concerns over his age, the economy and the war in Gaza.

Targeting a historic comeback, Trump told cheering supporters at his Mar-a-Lago beach club in Florida that they had witnessed "an amazing night and an amazing day."

"They call it 'Super Tuesday' for a reason," said Trump. "They tell me, the pundits and otherwise, that there has never been one like this, never been anything so conclusive."

Trump also launched an attack on the man who beat him in 2020, painting a dark picture of a second Biden term and describing him as weak on the immigration, the economy and foreign affairs.

'Personal grievance'

This year's Super Tuesday was sapped of suspense as Biden and Trump had effectively secured their parties' nominations before a ballot was cast.

A favorite of affluent, moderate Republican voters, Haley failed to derail Trump's path to the nomination since finishing a distant third in the opening contest in Iowa in January.

Impeached twice, beaten by seven million votes in 2020 and facing 91 felony charges in four trials, Trump has a profile unlike any US presidential election candidate in history.

Yet his appeal among working-class, rural and white voters has propelled him toward the nomination in one of the most lopsided primary seasons ever seen.

"This means the campaign will continue to be Trump's tour of personal grievance," Todd Belt, a politics professor at George Washington University, told AFP

Trump's victories included Maine, one of three states that had sought to keep him off the ballot over his push to overturn the 2020 election and the assault on the US Capitol. The Supreme Court rejected the expulsion effort Monday.

While he has not yet technically secured all the delegates he needs to be named at the Republican party summer convention, Trump's campaign expects to be anointed by March 19 at the latest.

Warning signs

Biden meanwhile raced to clear wins -- minus a loss in tiny Pacific Ocean territory American Samoa -- and warned that Trump was "determined to destroy" US democracy.

Biden is now expected to use his State of the Union speech in less than 48 hours to paint the election as a choice between himself and an existential threat to the country.

But while the election is set to be a rematch, recent polls give Trump a narrow lead, unlike four years ago when Biden was largely ahead ahead of the vote.

There are also warning signs from a protest vote over Biden's support for Israel's offensive on Gaza, with some voters filling out ballots saying "uncommitted" in Minnesota and other states.

Red lights are flashing for Trump too despite his dominant Super Tuesday performance, with signs that traditional voters in key swing states could be turned off by the chaos and scandal swirling around him.

Stephanie Perini-Hegarty voted for Biden in Quincy, Massachusetts.

"I think we need a leader who is not involved in any corruption, and who is going to look out for the best interests of the people," the 55-year-old told AFP.