Former presidential hopeful Nikki Haley said Wednesday she will vote for Donald Trump in the US election, but said her one-time bitter rival would have to work to win over her moderate support base as he faces President Joe Biden in November.

The former South Carolina governor, 52, abandoned her White House ambitions in March after suffering several heavy defeats in primary contests -- and had not previously indicated whether she would support the man who referred to her repeatedly as "birdbrain."

Despite having made withering criticism of the scandal-plagued ex-president, Haley said at an event for the Washington-based Hudson Institute, a conservative think tank, that she was urging Trump to make nice with her support base.

"Trump would be smart to reach out to the millions of people who voted for me and continue to support me and not assume that they're just going to be with him. And I genuinely hope he does that," she said.

More than two months after ending her White House campaign, Haley has continued to scoop a significant chunk of votes in presidential primary contests -- underlining a persistent refusal among a sizable bloc of Republicans to get behind Trump.

"I put my priorities on a president who's going to have the backs of our allies and hold our enemies to account, who would secure the border -- no more excuses -- a president who would support capitalism and freedom, a president who understands we need less debt, not more debt," she said.

"Trump hasn't been perfect on these policies. I've made that clear, many, many times. But Biden has been a catastrophe. So I will be voting for Trump."

- 'Zombie campaign' -

Trump and Haley traded at times vicious barbs during the state-by-state nominating contests, when the former UN ambassador warned that nominating her one-time boss would spell general election defeat for Republicans.

She said a majority of voters were opposed to a rematch between "chaos" candidate Trump and Biden, two men aged 77 and 81 respectively who she said were past their prime.

"He's getting meaner and more offensive by the day," Haley said ahead of a defeat in her home state of South Carolina in February.

"He's completely distracted, and everything is about him. He's so obsessed with his demons in the past that he can't focus on the future Americans deserve," she told supporters.

Haley criticized Trump's comments attacking NATO nations and referred repeatedly to the many court appearances he has been making as he faces multiple criminal indictments and lawsuits.

"It's not normal to spend $50 million dollars in campaign contributions on personal court cases," Haley said. "It's not normal to threaten people who back your opponent, and it's not normal to call on Russia to invade NATO countries."

Trump returned the compliment by categorically ruling her out of contention to be his running mate.

Trump has failed to make inroads with Haley's moderate backers, and will see her public show of support as a huge boon ahead of the Republican nominating convention in July.

The tenacity of the Haley vote long after she quit the race for the Republican presidential nomination prompted US media to refer to her ongoing presence on the primary stage as a "zombie campaign."

The primaries laid bare Trump's key shortcoming -- his lack of appeal among the moderates, independents and voters with college degrees he will need to prevail against Biden.

Meanwhile the Biden campaign had been reaching across the aisle, hoping to attract Haley voters.

It released a TV spot in April targeting suburban battlegrounds with the message: "If you voted for Nikki Haley, Donald Trump doesn't want your vote."

Judge hears bids to dismiss Trump charges

A Florida judge held hearings on Wednesday on bids by former president Donald Trump and his co-defendants to dismiss the charges they face for allegedly mishandling classified documents.

The hearings were held in Fort Pierce, Florida, before District Judge Aileen Cannon, who has indefinitely postponed Trump's criminal trial in the case.

Lawyers for Trump, who is seeking to recapture the White House in November, and his co-defendants -- his valet Walt Nauta and Mar-a-Lago property manager Carlos De Oliveira -- have filed multiple motions seeking to have the case thrown out.

Trump pleaded not guilty in Florida in June to the federal charges of unlawfully retaining national defense information, conspiracy to obstruct justice and making false statements.

He kept the classified files -- which included records from the Pentagon, CIA and National Security Agency -- unsecured at his Mar-a-Lago home in Florida and thwarted official efforts to retrieve them, according to the indictment.

Trump -- who is currently on trial in New York, accused in a separate case of falsifying business records to pay hush money to a porn star -- did not attend Wednesday's proceedings.

Cannon, a Trump appointee, first heard a motion filed by Nauta claiming that his prosecution was "vindictive" because he refused to cooperate with the investigation into Trump.

The judge did not immediately rule on the motion or on a second dismissal motion brought on behalf of all three defendants. Previous dismissal motions have been denied.

Wednesday's hearings were the first since Cannon, on May 7, indefinitely postponed the trial of the former president, which had been scheduled to begin this month.

Cannon said the planned May 20 start date was not possible because of the number of pre-trial motions before the court.

The postponement was a major setback for special counsel Jack Smith, who brought the charges against Trump, and makes it unlikely the case will be heard before the presidential election -- now less than six months away.

Trump's attorneys have sought to delay his various criminal cases until after the election, when Trump could potentially have the federal charges against him dropped if he wins.

In addition to the New York and Florida cases, Trump has also been charged in Washington and Georgia with trying to overturn the results of the 2020 election won by Democrat Joe Biden, his likely November opponent.