Donald Trump tightened his grip on the Republican presidential nomination with big wins in the "Super Tuesday" primaries, setting up an all-but-certain rematch with President Joe Biden in November.
Fifteen states -- including California and Texas -- were staging nominating contests on the biggest day of the 2024 race so far, with both candidates coveting a second term in the White House.
Texas was among a clean sweep of victories for Trump over Nikki Haley in the first ten states called, and he notably won comfortably in Virginia, taking one of his longshot challenger's best chances to win a state off the table.
This year's Super Tuesday had been sapped of much of its suspense as Biden and Trump had effectively secured their parties' nominations before a ballot was cast Tuesday.
Haley, a former UN ambassador, has failed to throw any significant obstacles in Trump's path to the nomination, losing every state since finishing a distant third in the first contest in Iowa in January.
Impeached twice, beaten by seven million votes in 2020 and facing 91 felony charges in four jurisdictions, Trump has a profile unlike any US presidential election candidate in history.
Yet his appeal among working-class, rural and white voters is expected to carry him to the nomination, with victories likely in most of the 15 contests on offer Tuesday -- if not a clean sweep.
Polling averages from RealClearPolitics show 77-year-old Trump two points ahead of Biden in a hypothetical one-on-one match-up.
Haley looks set to collect only a handful of the delegates needed to secure the nomination with her narrow support base of affluent, suburban university graduates.
"Today's her last day," physicist Andrew Pugel told AFP at a polling station in Huntington Beach, California, though he added that it would be smart of Trump to make her his running mate and "unite the country."
Trump's Super Tuesday 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 that he was impeached for inciting.
The Supreme Court rejected the expulsion effort on Monday, clearing the path for Trump's participation in every state.
The states up for grabs Tuesday offer 70 percent of the delegates Republicans need to be named the party's standard-bearer at the summer convention.
Trump would not be able mathematically to close out the contest but he expects to be anointed by March 19 at the latest, according to his campaign.
Biden is on the ballot in the Democratic primaries, but faces little threat from two outsider challengers, making his re-nomination a formality.
He is due to deliver the annual State of the Union address to Congress on Thursday, a chance to lay out his campaign platform.
The 81-year-old raced to easy wins after polling stations began closing on the east coast, and he quickly sent out a fundraising email as Trump began putting points on the board.
"It's going to be us vs. the entire MAGA right in this election, and it's going to take a big team to finish the job," the president said.
With some forecasts of a low turnout, pop star Taylor Swift urged people to vote in an Instagram message. She did not endorse any candidate, though Democrats hope she will publicly back Biden in November.
Trump has made clear he is looking past the primaries to Election Day, but Haley's campaign questions whether middle-of-the-road Republicans are drifting away from him.
Some primary-watchers expect Haley, 52, to end her campaign after Super Tuesday, although she could forge on.
The ex-president has spent nine days in court this year alone -- although he has turned court appearances to fire up his supporters.
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.
