Live Updates: Michael Cohen, Trump’s Ex-Fixer and His Nemesis, to Testify at His Trial

This week, however, Mr. Cohen is poised to unfix Mr. Trump’s life. When he takes the stand as a vital witness at Mr. Trump’s criminal trial in Manhattan, Mr. Cohen will unearth some of the secrets he buried, revealing a mess that prosecutors say his former boss was desperate to hide.

It will represent a pivotal moment of the trial, and the climax of a decades-long relationship between two New York loudmouths who used each other, betrayed each other and will now face off on the biggest stage: The first criminal trial of an American president.

Interviews with 10 of Mr. Cohen’s allies and adversaries, as well as a review of court records and Mr. Cohen’s books, paint a portrait of a once-obscure operator who came to play an outsized role in American politics, a man whose relationship with the former president traced an arc from asset to threat.

From the stand, Mr. Cohen will tell of his greatest coup in Mr. Trump’s employ, the time when he paid $130,000 to suppress a porn star’s story of a sexual encounter with Mr. Trump. He did so, he will say, at his boss’s direction. And, illuminating what prosecutors say is the cover-up at the heart of the case, he is expected to offer his firsthand account of how, after the 2016 election, the new president reimbursed him for the hush money, but falsified records to disguise those payments as legal expenses.

Mr. Trump denies any role in falsifying the records, and says he never had sex with the porn star, Stormy Daniels. His lawyers dispute that any crime occurred.

Despite months of preparation, Mr. Cohen, 57, will be unpredictable on the stand, prone as he is to both tirades and charm.

Prosecutors acknowledged on Friday having little control over Mr. Cohen, who, despite their admonitions, has taunted Mr. Trump throughout the trial. In a recent TikTok video, Mr. Trump’s lawyers complained, he wore a shirt with a picture of the former president behind bars, prompting the judge to request that he keep quiet.

But prosecutors, who are offering Mr. Cohen nothing in return, have little leverage to rein him in. Unlike a traditional cooperating witness who trades testimony for leniency, he has already spent more than a year in federal prison for paying the hush money and committing other crimes.

That experience, contrasted with that of other Trump aides who avoided indictment or received pardons, has catalyzed his anger. Mr. Cohen, whose self-image remains inextricably tied to Mr. Trump, has transformed himself from lackey to antagonist, adopting a new identity, but with the same personality.

Craving public redemption, Mr. Cohen has fashioned himself as a standard-bearer of the anti-Trump resistance, seeking what he once called a “way to right some of the many wrongs I committed at his behest.” And since his prison stint, he has made money from their feud. There have been books bluntly titled “Disloyal” and “Revenge,” and a podcast called “Mea Culpa.”

Under questioning from prosecutors, his testimony could play out like a cinematic thriller, as he casts himself as a consigliere turned state’s evidence. This is the story Mr. Cohen told when he testified before Congress, where he estimated he had made 500 threats at Mr. Trump’s behest, and at a New York civil trial, where he accused the former president of fraud.

At that trial, the defense accused Mr. Cohen of perjury. Now, Mr. Trump’s team in the criminal case is expected to escalate those attacks, painting Mr. Cohen as a rogue actor whose fixes caused more problems than they solved. They have promised to seize on Mr. Cohen’s credibility and criminal record — Mr. Trump is fond of noting that he is a “convicted liar” — and portray him as a scorned underling seeking revenge against the former president.

Prosecutors from the Manhattan district attorney’s office have already anticipated those lines of attack — and leaned into them. While the prosecutors introduced witnesses to corroborate much of Mr. Cohen’s account, they have invited those same witnesses to cast him as a bully, a nervous wreck and, as one person put it, a “jerk.”

The intent is to suck the air out of the defense’s attacks and desensitize the jury to Mr. Cohen’s baggage, turning him into an object of amusement. Already, his name has drawn smiles from some of the jurors, who will now evaluate his credibility for themselves.

“He was everything Trump wanted,” said Donny Deutsch, a television personality and advertising executive who is close with Mr. Cohen and was once friendly with Mr. Trump. “He’s aggressive, he’s tenacious, he’s a bulldozer, and so what you’re hearing in court, a lot of the perceived negatives, is what made him a positive for Trump.”

Mr. Deutsch recalled that, years ago, after he had implied on television that Mr. Trump was racist, Mr. Cohen called to complain. “Donald is really upset,” Mr. Cohen said. “Can you talk to him, tell him you don’t think he’s a racist?”

Mr. Cohen, who learned from and parroted his boss, acknowledged in his memoir that he had been Mr. Trump’s “designated thug.”

Their relationship, defined by abuse and subservience, imploded soon after the hush-money deal came to light in 2018. Mr. Trump washed his hands of Mr. Cohen, who in turn vowed to flip.

Ever since, they have waged public combat with one another. Mr. Trump sued Mr. Cohen and called him a “rat.” Mr. Cohen sued Mr. Trump and called him a “mob boss.”

But, as the trial approached, people close to him say, Mr. Cohen’s notoriety as a Trump nemesis took a personal toll that left him anguished. He privately conveyed a fear for his safety, though he ultimately concluded he had no choice but to testify.

After the trial started, Mr. Cohen pledged to “sit my ass in that witness stand,” and “just tell the truth.”

‘He said he was a lawyer.’

Mr. Cohen, the son of a Holocaust survivor, had idolized Mr. Trump since his youth on Long Island. And after buying apartments in two of Mr. Trump’s New York buildings in the early 2000s, he caught Mr. Trump’s eye during a dispute with the condo board at Trump World Tower in New York.

Mr. Trump saw his potential as an enforcer, and soon Mr. Cohen received an office on the 26th floor of Trump Tower.

But Mr. Cohen’s colleagues at the Trump family real estate business saw his job as something of a mystery. They spotted him inside Mr. Trump’s office, overheard him yelling from his own and watched him walk the hallways with a pistol strapped to his ankle.

A prosecutor last week asked a former co-worker about Mr. Cohen’s precise position at the company, the Trump Organization.

“He said he was a lawyer,” Jeffrey McConney, Mr. Trump’s former corporate controller, replied dryly, eliciting laughter from the courtroom.

Mr. Cohen was indeed a lawyer, in the sense that he had graduated from law school, worked as a personal injury lawyer and occasionally performed tasks that approximated legal work under the amorphous title of executive vice president of the Trump Organization and “special counsel” to Mr. Trump.

But more often than not, Mr. Cohen’s tasks were unrelated to the law — and sometimes, at odds with it.

There was the time, Mr. Cohen recounted in “Disloyal,” that he threatened to tank a paint company with bad publicity to get thousands of gallons of free paint for Mr. Trump’s golf resort outside Miami.

And the time Mr. Cohen hired a computer programmer to rig an online CNBC poll to ensure that Mr. Trump would rank among the most influential business people alive.

And the time he threatened to ruin the college admission prospects of a child whose family was a tenant in a Trump building, so that they would not obstruct a renovation.

Mr. Cohen never much liked the term fixer. But the role had special meaning to Mr. Trump, who was always on the lookout for someone to emulate his earliest lawyer, Roy M. Cohn, an unscrupulous defender known for scorched-earth tactics honed while working for Mafia bosses and the Communist-hunting Senator Joseph McCarthy.

Mr. Cohen updated the part for the digital era, helping Mr. Trump draft some of his nastiest social media snipes, not at political enemies, but instead at fellow celebrities such as the actress Rosie O’Donnell.

He also scouted the occasional deal, including foreign projects that never materialized, like a plan for a Trump Tower in Moscow that caught the interest of federal investigators and ultimately led to one of Mr. Cohen’s guilty pleas. (He admitted to lying to Congress about the deal out of loyalty to Mr. Trump.)

Mr. Cohen also protected the Trump family, emails and other records show. He helped Mr. Trump’s youngest son, Barron, find a private school. He helped his oldest, Donald Trump Jr., dig out of an ill-fated business venture. And, on occasion, Mr. Cohen has said, Mr. Trump put Mr. Cohen on the phone with his wife, Melania, to reassure her that he hadn’t been unfaithful.

In return, Mr. Trump subjected Mr. Cohen to ridicule. Over their decade together, Mr. Trump stiffed him on bonuses and threatened to fire him at least twice.

But Mr. Cohen kept searching for new ways to win the dollops of approbation he craved, including by nurturing his nascent political hopes.

Mr. Cohen, who indulged his own political aspirations as a failed City Council candidate, was one of the strongest believers in Mr. Trump as a possible president when he flirted with running in 2012. Mr. Cohen set up a website, ShouldTrumpRun.org, and went on a scouting trip to Iowa.

Although he had no formal role on the 2016 campaign, Mr. Cohen nonetheless raised millions of dollars, recruited Black supporters and was an enthusiastic booster of Mr. Trump on television.

But his greatest service came behind the scenes, arranging payoffs to two women who had threatened to go public with stories about having sex with a married Mr. Trump. One, Karen McDougal, struck a $150,000 deal with Mr. Trump’s allies at The National Enquirer, who bought and buried the former Playboy model’s story.

The second woman was the porn star, Ms. Daniels, who described her encounter with Mr. Trump in graphic detail on the witness stand last week. When Mr. Trump was slow to pay the $130,000 hush money, Mr. Cohen dug into his own pocket.

Mr. Trump repaid him monthly through the first year of the presidency. Mr. Cohen was no longer a Trump Organization employee, and Mr. Trump had excluded him from a job in Washington. But Mr. Cohen’s email signature now carried a loftier title: personal lawyer to the president.

When one of Mr. Trump’s friends asked Mr. Trump why he kept Mr. Cohen so close, Mr. Trump replied, “He has his purpose.”

The knock at the door

In the early morning hours of April 9, 2018, as Mr. Cohen puttered around a New York hotel room sipping coffee in a pair of Nike shorts, he heard a knock on the door.

Peering through the peephole, he saw a row of badges. It was the F.B.I.

The swarm of agents was at the hotel, where Mr. Cohen was staying while his apartment was undergoing repairs, with a warrant to seize evidence of various crimes, including that the hush money had constituted an illegal donation to Mr. Trump’s campaign. By midday, they had also searched his office, his home and his safe deposit box.

People who saw Mr. Cohen afterward described a suicidal man who paced the room, refusing to spend a single day in jail.

Mr. Trump was enraged as well. On the day of the search, he declared it “a disgraceful situation.”

Initially, Mr. Trump came to Mr. Cohen’s defense, publicly flattering Mr. Cohen as a “good man” and privately phoning him with a message: Stay strong. The support soon faded, the phone stopped ringing and the public praise dried up.

Not even a month after the raid, Mr. Trump called into one of his favorite television shows, “Fox & Friends,” and distanced himself, saying Mr. Cohen had handled just “a tiny, tiny little fraction” of his legal work. Mr. Trump added: “From what I understand, they’re looking at his businesses,” nodding to the tax and bank crimes to which Mr. Cohen would ultimately plead guilty.

By June, Mr. Trump’s company used that same logic to stop paying Mr. Cohen’s mounting legal bills. It was the final straw for Mr. Cohen, who hired Lanny J. Davis, a veteran Washington lawyer and public relations strategist with close ties to Democratic politicians. He also told friends that he was willing to cooperate with prosecutors.

When he pleaded guilty to federal charges that August, Mr. Cohen for the first time stood up in a courtroom to accuse the man he had once protected, saying he had paid the hush money “at the direction of” his former boss.

He told a judge, while being sentenced to prison, “I felt it was my duty to cover up his dirty deeds.”

In 2020, Mr. Cohen was released on furlough during the coronavirus pandemic. But the Federal Bureau of Prisons sent him back behind bars in Otisville, N.Y., after he refused to sign paperwork barring him from publishing a book during the remainder of his sentence. A judge later called his second imprisonment “retaliatory.”

His friends say he remains tortured.

“He doesn’t revel in any of this,” said Omarosa Manigault Newman, a former White House aide. “If Michael had his way, he would still be working with Trump.”

‘You’re not on your podcast.’

At first, the performance was surprisingly smooth.

Mr. Cohen took the stand at Mr. Trump’s civil fraud trial in October 2023 and did what the New York attorney general had asked: He testified that Mr. Trump had directed him years earlier to manipulate internal records to make the developer look richer than he was.

Then it was the defense’s turn.

Alina Habba, Mr. Trump’s lawyer, paced in front of the bench. She smiled as she reintroduced herself to Mr. Cohen and, minutes later, attacked him as a disgraced former lawyer and a serial liar who had perjured himself even while pleading guilty to a federal crime.

“You have lied under oath numerous times, Mr. Cohen, isn’t that correct?” Ms. Habba asked. Mr. Cohen acknowledged that it was.

He fought back, noting that when he had lied in court, he had often done so for Mr. Trump. He even lodged his own objections, citing legal precedents, though he had lost his law license after pleading guilty years earlier.

“You don’t get to object,” Ms. Habba told him, later reminding him, “You’re not on your podcast.”

Though the judge found that Mr. Cohen had been “credible,” his unpredictability on the witness stand stood as a cautionary tale for prosecutors in Mr. Trump’s criminal case.

Anticipating attacks on his credibility, the prosecutors have sought to corroborate his story during the first three weeks of testimony, introducing evidence in support of his assertion that Mr. Trump directed the hush-money deal.

Hope Hicks, Mr. Trump’s former spokeswoman, scoffed at the notion that Mr. Cohen would have made the $130,000 hush-money payment to Ms. Daniels out of the kindness of his heart because doing so “would be out of character for Michael,” an insulting comment that nonetheless supported Mr. Cohen’s story.

They also elicited testimony from another former Trump aide who confirmed that Mr. Cohen was scheduled to meet with Mr. Trump in the White House in early February 2017. At that meeting, Mr. Cohen has said, he and Mr. Trump confirmed their plan to falsify the records.

And prosecutors made sure to enter into evidence the voice of a man who had once found Mr. Cohen essential.

“Michael Cohen is a very talented lawyer,” Mr. Trump said, in a recording from a news conference in 2017 that was played in the courtroom. “He’s a good lawyer at my firm.”