It has long been considered that making a movie about Donald Trump was virtually impossible, if not for the divisive subject material itself, but because the former US president was already playing that character to the hilt – and sometimes beyond.

But last week, the Cannes film festival announced that it was adding the Iranian-Danish film-maker Ali Abbasi’s The Apprentice to its 2024 official film selection for the event’s main competition.

The drama stars Sebastian Stan as Trump in his years on the make in the 1970s as a New York property developer and his mentor-protege relationship with the lawyer-political fixer Roy Cohn, played by Succession’s Jeremy Strong.

Cohn is one of the darkest backroom figures in US politics who began his career working with Senator Joseph McCarthy in the late 1950s as he investigated alleged communist influence within the press and the federal government and participated in sending the Rosenbergs to the electric chair for spying.

Abbasi, the writer-director best known for Border (2018), Holy Spider (2022) and Shelley (2016), traces the start of Trump’s American dynasty, taking a “dive into the underbelly of the American empire” and “charts a young Donald Trump’s ascent to power through a Faustian deal with the influential rightwing lawyer and political fixer Roy Cohn”.

The film also stars Maria Bakalova as Ivana Trump, and Martin Donovan as Donald Trump’s father, Fred, from a script penned by the Vanity Fair writer Gabriel Sherman, author of a biography of the Fox News founder Roger Ailes.

In all likelihood, the Cannes premiere will come while the real Donald Trump is still in court in Manhattan on charges that he covered up payments to the adult movie star Stormy Daniels and Playboy model Karen McDougal, which the New York County attorney general, Alvin Bragg, charges rise to the level of campaign finance violations.

However the case is decided, there is little doubt that Trump might believe he has need of Cohn, who died of complications from Aids at the age of 59 in 1986, more than ever.

Cohn, a master of the attack and counterattack, is sometimes referred to as Trump’s alter ego and machiavellian, and was described by Vanity Fair in 2019 as a “wily, menacing lawyer who had gained national renown, and enmity, for his ravenous anti-Communist grandstanding” and was famous for saying: “Fuck the law, just tell me who the judge is.”

But to Trump, he was a guide for a young man who came from the outer boroughs who did not know how the Manhattan scene worked and was able to manipulate politicians and prosecutors, protect mob bosses, and cultivate the press to make stories appear or disappear as needed.

In a fascinating biography, Roy Cohn, published two years after Cohn’s death, the New York Post writer Sidney Zion described how Trump, despite raising $300,000 for the Democratic mayor Ed Koch, had been denied a tax exemption, an abatement, for his 5th Avenue Trump Tower. Cohn fixed the problem.

Later, Cohn called on Trump to help him pay off a judgment related to damage to the cabin of a chartered airplane that Cohn and his young lovers had trashed en route to Paris. “I felt sorry for the poor bastard,” Trump was quoted as saying, “because Roy just wiped out that plane. But … hey, it was Roy, what’s anybody supposed to do?”

Cohn was not interested in money, according to Zion, but the trading of favors, or “markers”, as he called them. Trump said he didn’t charge clients or almost never charged them enough. “Roy charged me less than any lawyer I’ve had,” the former president recalled.

Bob Colacello, the former Interview editor and Vanity Fair writer, recalls going to Cohn’s annual Fourth of July party in Greenwich, Connecticut, with Andy Warhol. The rising names of New York were all there: the young Donald Trump, the young Ron Perelman, Estee Lauder, his school friend and Condé Nast publisher SI Newhouse, but also Carmine DeSapio, the last head of the Democratic Tammany Hall political operation, and all the Democratic borough presidents of the city.

“I think he had a lot to do with Donald Trump’s rise because if you’re in the real estate business in New York, you need the city and the state for permits and tax abatements, and Roy was the ultimate fixer. He could navigate these things,” Colacello said.

So when the Trump of today rants about a witch-hunt, and disparages the prosecutors and the judges presiding over his cases, it could be just because there’s no Cohn around to have sorted it out.

“Roy knew his way around all this,” says Colacello. The trial starting on Monday could end up giving Trump more publicity than his campaign rallies ever could – and as Warhol said, success is measured in column inches.

“Roy Cohn would have gone over the head of the DA, or to the big-money people on the Democratic side, pulled his strings and been able to persuade them that this wasn’t worth it and would just contribute to making him a martyr. He was persuasive and he had things on people,” said Colacello.

“It’s hard to say what Cohn would have done, but you didn’t hire him when you wanted a nice, white-shoe lawyer to do a very correct kind of case,” he adds. “You hired Roy Cohn when you wanted the toughest guy in town. People might have called him a thug but you hired him because he was a thug and he knew how to deal with the other thugs that ran the city. It’s not an illustrious group.”

• This article was amended on 22 April 2024. Alvin Bragg is the district attorney for New York County (Manhattan), not New York City.