Trump and Biden rematch looms as both win big

Donald Trump vowed to cheering supporters that he would "take back our country" after dominating the Super Tuesday primary contests.

Hours later he became the only Republican left in the presidential race with rival Nikki Haley set to formally drop out on Wednesday.

Meanwhile, President Joe Biden largely sailed through the Democratic nominating contests.

The results make a repeat of the 2020 US election all but certain.

Both men appear poised to frame the election as an existential test for the future of the country as they head towards a rematch in November.

Polling indicates that many Americans do not want the same choice they had four years ago but the Super Tuesday results make that all but certain.

Despite the lack of enthusiasm, both men swept nearly all of the contests as voters in 15 states and one territory cast their ballots on the biggest night in the primary calendar.

Mr Trump won in Alabama, Arkansas, California, Colorado, Maine, Massachusetts, Minnesota, North Carolina, Oklahoma, Tennessee, Texas and Virginia.

He lost in Vermont to former UN ambassador Ms Haley, who will announce she is quitting the race on Wednesday, according to the BBC's US partner CBS News.

Mr Biden swept the same states plus Utah and Vermont, but lost to a Baltimore businessman in the US territory of American Samoa. He also won the Iowa caucus, which announced its results on Tuesday.

As the two candidates racked up their wins on Super Tuesday, they characterised each other as threats to the US.

Mr Trump warned his supporters at Mar-a-Lago that if "we lose the election, we're not going to have a country left".

He invoked one of his key issues, immigration, and the numbers crossing the southern border. He also pledged that the world would see fewer wars if he were president.

Just before Mr Trump spoke, Mr Biden released a statement saying his opponent was "driven by grievance and grift," rather than by his concerns for the country.

"Tonight's results leave the American people with a clear choice," he said. "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?" he said.

Analysts are viewing the Super Tuesday primaries as a test of Mr Biden and Mr Trump's support in different states and among different groups. It is also a test for the parties and their voters' enthusiasm.

There were several other important takeaways on Tuesday night:

By the end of Super Tuesday, Democrats and Republicans will have awarded about a third of the total delegate count available through the entire primary contest.

The Trump campaign is confident the former president will hit the delegate threshold later this month.

Mr Biden and Mr Trump have all but locked up their parties' nominations but there were warning signs for both.

The president has seen some Democratic voters back "uncommitted" on ballots and while it is unclear how that may translate in November, it could chip away at his support in key states.

On the Republican side, many anti-Trump voters had given their backing to Ms Haley.

She did not hold a campaign event after failing to gain huge traction on Tuesday night, but her campaign emphasised that her Republican supporters - who could prove key in a general election - continue to seek an alternative to Mr Trump.