Donald Trump has spent the night at his golf club in Doral just outside Miami ahead of his historic federal court appearance.
The former president will appear at the Wilkie D. Ferguson Court House at 3pm (8pm UK time) on charges he stole classified documents and lied to block efforts to get them back.
Trump touched down in his private plane on Monday afternoon.
A small group of supporters gathered outside the Trump National Doral Miami golf resort, cheering as his motorcade drove past.
He faces 37 felony counts over documents found at Mar-a-Lago, his Florida home, as well as claims he obstructed justice and made false statements.
Pictures released by the Department of Justice as part of its unsealed indictment showed boxes of documents stacked inside his Mar-a-Lago estate, including in a bathroom.
Details on nuclear weapons programmes, potential vulnerabilities of the US and its allies, and plans for retaliatory military attacks were in some of the documents, according to prosecutors.
Roughly 13,000 documents were seized in raids on the property nearly a year ago. One hundred of them were marked as classified.
Prosecutors say Trump’s hoarding of papers from his time as president jeopardised national security – and the Espionage Act charges carry the prospect of up to 20 years in jail.
Writing on his Truth Social site before boarding his flight, he said: “I hope the entire country is watching what the radical left are doing to America.”
However some of Mr Trump’s Republican challengers for the presidential nomination appear to be shifting their tone.
Speaking to Fox News, Nikki Haley said: “If this indictment is true… President Trump was incredibly reckless with our national security… This puts all of our military men and women in danger.”
It is the first federal indictment of a former president, but Mr Trump claims he is being persecuted in an attempt to stop him becoming president again in 2024.
Polls suggest his supporters overwhelmingly believe the charges are politically motivated.
In a weekend CBS News poll of Republican voters, just 12% said their biggest concern about the indictment was the fact that the documents posed a national security risk.
More than three-quarters (76%) said their biggest concern was that the indictment is politically motivated.
Protesters in Miami raised allegations about President Biden’s mishandling of classified documents, which remain under investigation, and the Hilary Clinton email scandal.
But speaking to Sky News, a former federal prosecutor who almost prosecuted Richard Nixon over Watergate, and declined to represent Donald Trump last year said there were distinct differences between the cases.
“The big difference is cooperation,” Jon Sale said.
“When President Trump was served a subpoena last spring, if he had told his lawyer, ‘Look, I want to turn over everything; I want to comply with the subpoena. Do a diligent search – everything we have, turn it over to the grand jury’, then you and I wouldn’t be here today.”
Miami police’s chief said he was expecting up to 50,000 people on the streets for today’s hearing and that downtown roads could be closed if necessary.
The former president will be fingerprinted. He will have a mugshot taken but it will not be released and there will be no cameras of any sort in the courtroom itself. He will have the charges read out to him and enter a plea. The case will then be adjourned.
Mr Trump, who turns 77 this week, is also due to go on trial next March over separate claims that he falsified business records to conceal damaging information and unlawful activity. And there’s another case against him in Georgia for his alleged efforts to overturn the 2020 election.
Scheduling for the three trials could mean that this case is not completed before the November 2024 presidential election.