Michael Cohen once described himself as Donald Trump’s “spokesman, thug, pit bull and lawless lawyer.”

But this week, he has a new role. He will be the star witness for prosecutors trying to prove Trump illegally falsified business records after paying off adult film actress Stormy Daniels as part of an alleged election interference scheme in 2016.

Cohen’s testimony is set to be the critical moment of the hush money trial that could make Trump the first ex-president to be convicted of a crime. His appearance will mark the zenith of a bitter personal feud between two brash New Yorkers obsessed with betrayal and revenge. And it marks one of the most lurid twists yet in the presumptive Republican nominee’s legal morass that is entwined with the 2024 election.Trump’s former fixer wrote in his autobiography that he craved reflected influence and notoriety from Trump, so he adopted the real estate magnate’s methods — including bullying, lying and mocking the rule of law — to serve him. He once vowed to take a bullet for his boss. But his testimony will be his latest attempt to atone for this Faustian pact after he paid the price, including with a spell in prison, for his years as a kingpin in Trump’s orbit.

In many ways, Cohen is the mirror image of Trump — a colorful braggart and social media provocateur who craved power and riches and was prepared to pay any price and to intimidate anyone to get them. Cohen, who worked for the Trump Organization cleaning up the mess from the family’s personal scandals and busted business deals, facilitated the $130,000 hush money payment to Daniels, he says, on the orders of his boss. Trump has denied having an affair with Daniels, whose testimony last week about their alleged liaison at Lake Tahoe in 2006 seemed excruciating for the ex-president. He has pleaded not guilty in this case and to three other criminal indictments.

Cohen’s value as a witness is that he was involved in every aspect of Trump’s business and personal life, knew all his secrets, and was allegedly an accessory in his efforts to break the law and thwart accountability. In his book “Disloyal,” Cohen wrote, “I know where the skeletons are buried because I was the one who buried them.”

Prosecutor Matthew Colangelo said in his opening statement that “Cohen made that payment at the defendant’s direction, and he did it to influence the presidential election.” After the election, Trump is accused of working out a scheme in the Oval Office to reimburse Cohen for the hush money payment in installments disguised as billing for legal services. “The defendant falsified those business records because he wanted to conceal his and others’ criminal conduct,” Colangelo said, adding that both Cohen and the prosecution will be up-front about mistakes Cohen has made in the past.

Cohen’s friend and fellow former Trump acolyte Anthony Scaramucci, who briefly served as the ex-president’s White House communications director, said the former fixer will be able to prove the criminality of campaign interference. “I think unfortunately for Donald Trump, Michael Cohen has the receipts for everything that went on,” he told CNN’s Jake Tapper on Friday. “They’re smoking gun receipts, and he’s going to provide very compelling, very honest, very direct testimony.”