Prosecutors allege that at first, Cohen and Trump tried to delay the payment until after the election, but ultimately Cohen made the payment by taking out a line of credit on his personal home and wiring the money to Daniels’ lawyer.

After Trump became president, he reimbursed Cohen through his company, but allegedly disguised the payment as a legal retainer. It’s this payment – intended to hide details from voters – that breached campaign finance laws, according to prosecutors, who have framed this case as election interference.

Could Trump end up in jail?

The charges Trump faces come with a maximum sentence of four years each so, theoretically, the former president could be sentenced to a hefty jail term if he is convicted (sentencing for this particular felony would be capped at 20 years).

However, the charges involve non-violent offences and, given that Trump does not have a criminal record, the judge could also consider a lenient sentence or even place him on probation, with the prospect of jail hanging over his head if he fails to abide by certain conditions.

That said, the case brought by Manhattan District Attorney Alvin Bragg is far from a slam dunk. That’s because, on its own, the falsification of business records in New York is usually regarded as a misdemeanour. It only gets elevated to a felony if the falsification of those records took place to conceal another crime.

To that end, Bragg must convince a jury that Trump’s crime was to cover up a campaign contribution – the “contribution” effectively being Daniels’ silence.

It’s a novel and somewhat convoluted approach that has left Bragg, a Democrat, exposed to criticism that he is performing legal gymnastics in order to secure a conviction against Trump, who has repeatedly argued that he is the victim of a political witch hunt.

Bragg argues that no one is above the law. The core of the case “is not money for sex”, he told WNYC radio recently.

“We would say it’s about conspiring to corrupt a presidential election and then lying in New York business records to cover it up.”

What is Trump’s defence strategy?

Trump has consistently denied any wrongdoing and even rejects claims he slept with Daniels, who has publicly spoken about their encounters in intimate and salacious detail.

In a social media post in 2018, the then president admitted reimbursing Cohen with a monthly retainer but insisted it had “nothing to do with the campaign”. His legal team is widely expected to attack Cohen, who has admitted to previously lying in court and to Congress.

Since being indicted last year, Trump has also repeatedly sought to delay the case, pushing to remove presiding judge Juan Merchan or have the trial relocated out of Manhattan – a Democrat stronghold that voted overwhelmingly for Joe Biden at the last election.

The former president has also made his legal woes a central part of his pitch for re-election, depicting himself as the victim of political persecution.

“They think they can lock me up for life when their rigged trials start tomorrow,” he wrote in a fundraising email seeking donations ahead of tomorrow’s trial, which he described as the darkest day in American history.

“But with you by my side, I WILL NEVER SURRENDER!”

Who will testify?

Michael Cohen, the former president’s fixer-turned-foe, will obviously be a star witness for prosecutors.

Cohen pleaded guilty in August 2018 to two campaign finance violations, claiming that he made hush money payments at Trump’s direction “for the principal purpose of influencing” the election.

One of those payments relates to Stormy Daniels, while the other involves a $US150,000 payment made to former Playboy playmate Karen McDougal, who also says she had an affair with Trump before he became president.

The National Enquirer bought the rights to McDougal’s story in order to silence it – a practice known as “catch and kill”.

Both women are also expected to testify, along with David Pecker – the former chief executive of American Media Inc, which published the National Enquirer – and its tabloid editor, Dylan Howard.

Other potential witnesses include former Trump aide Hope Hicks, former personal secretary Madeline Westerhout, who worked with Trump in the White House, and Daniels’ former lawyer, Keith Davidson.

Trump is not required to testify but claimed on Friday he was “absolutely” willing to do so – something even his supporters say could be risky.

What about Trump’s other trials?

Loading

All up, Trump faces four criminal trials and a combined 88 charges (he originally had 91 charges but three have since been quashed).

There’s a trial in Washington over his attempt to stop Joe Biden’s victory from being certified, another in Georgia over election subversion in that state, and another in Florida over his handling of classified documents.

However, those cases are not yet firmly scheduled as Trump has gone to great lengths to delay them.

This particular case, which centres on events that took place years ago, was initially viewed by many as the least serious indictment Trump faces. Now, however, it is the first to go to trial – and it could be the only one to hold him to account before election day.

Get a note directly from our foreign correspondents on what’s making headlines around the world. Sign up for the weekly What in the World newsletter here.