Michael Cohen is an admitted liar. He’s still going to be the star witness against Trump.

NEW YORK — By his own admission, he has lied in court. He has lied to the media. And he has pleaded guilty to lying to Congress.

Now, he’s set to be state prosecutors' key witness against Donald Trump.

Michael Cohen, the former president’s fixer-turned-foe, is expected to tell jurors in the criminal trial starting Monday that Trump directed him to pay $130,000 in hush money to porn star Stormy Daniels so that she wouldn’t go public in the final weeks of the 2016 election with an allegation about a sexual encounter with Trump. Prosecutors have accused the former president of falsifying business records reflecting Trump’s reimbursements to Cohen.

But while the prosecution’s ability to prove its case at trial could hinge on Cohen’s first-hand account of the hush money arrangement, Cohen also may be its most problematic witness due to long-running questions about his ability to tell the truth.

“If a jury doesn’t believe him, that’s it,” said Catherine Christian, a former Manhattan assistant district attorney.

Cohen’s credibility has undoubtedly been tarnished over the years, but it was recently redeemed by a judge in a different Trump trial: the New York attorney general’s civil lawsuit in which the former president was found liable for corporate fraud. Cohen’s testimony about Trump’s practice of inflating the value of his assets helped result in a half-billion dollar judgment against Trump.

“Michael Cohen told the truth,” Justice Arthur Engoron, who oversaw the fraud case, wrote in February about Cohen’s testimony there.

And as Cohen himself recently told POLITICO, when he lied to a Senate committee in 2017, he did so solely for the purpose of benefiting his then-boss, Trump.

Cohen pleaded guilty in 2018 in two federal cases to a handful of crimes, including campaign-finance violations stemming from the hush money payments, tax evasion and making false statements to Congress. He was sentenced to three years in prison.

But becoming a convicted felon was just the beginning of his credibility problems.

Soon after his guilty pleas, Cohen began saying publicly that he hadn’t committed tax evasion, despite having told a federal judge, U.S. District Judge William Pauley, in court that he had. And when Cohen attempted to get his sentence reduced, federal prosecutors said they had “substantial concerns about Cohen’s credibility as a witness” and that, following his sentencing, he “made material false statements” during meetings with prosecutors and the FBI. Prosecutors declined his offer to meet with them again.

Then, last fall, Cohen faced Trump for the first time since their split, testifying in New York state court in the civil fraud trial against the former president. During that testimony, Cohen again remarked — this time, under oath — that he hadn’t committed tax evasion. And he said he had lied to the judge when pleading guilty.

“So, sir, you lied at the time — you lied more than once in federal court, correct?” Trump lawyer Alina Habba asked Cohen. He replied: “Correct.”

He also testified that he had cooperated with the government and had “refused” a letter from federal prosecutors in which they would have argued for him to receive a lighter sentence in exchange for his cooperation. Federal prosecutors, however, have said in court filings that Cohen’s assistance “fell well short of cooperation” and therefore he wasn’t offered a cooperation agreement or a corresponding letter.

After his testimony in the civil fraud case, federal prosecutors told a judge that Cohen “has continued to deny responsibility for his own criminal conduct, and appears to have lied under oath in a court proceeding.”

In court filings in the Manhattan criminal case, Trump’s lawyers have fixated on Cohen. They asked Justice Juan Merchan to bar District Attorney Alvin Bragg’s office from calling Cohen as a witness. They have argued that Cohen committed perjury in state court and that questioning him as a witness in Trump’s criminal trial would induce Cohen to commit “further perjury.”

“Michael Cohen is a liar. He recently committed perjury, on the stand and under oath, at a civil trial involving President Trump,” Trump lawyers Todd Blanche and Susan Necheles wrote. “If his public statements are any indication, he plans to do so again at this criminal trial. The Court should preclude Cohen’s testimony in order to protect the integrity of this Court and the process of justice.”

Merchan denied their request to exclude Cohen as a witness, writing that he “has been unable to locate any treatise, statute, or holding … that supports Defendant’s rationale that a prosecution witness should be kept off the witness stand because his credibility has previously been called into question.”

And yet, despite Cohen’s rocky record, he has been somewhat redeemed.

In the verdict against Trump in the civil fraud case, Engoron acknowledged that Cohen’s testimony “was significantly compromised by his having pleaded guilty to perjury and by some seeming contradictions in what he said at trial.” Still, the judge wrote that he ultimately found Cohen’s testimony “credible, based on the relaxed manner in which he testified, the general plausibility of his statements, and, most importantly, the way his testimony was corroborated by other trial evidence.”

“This factfinder does not believe that pleading guilty to perjury means that you can never tell the truth,” Engoron wrote.

And even critics of the district attorney’s office have said they believe Cohen can overcome any credibility concerns. Mark Pomerantz, a former special assistant district attorney who investigated Trump and consequently interviewed Cohen numerous times, wrote in his book “People vs. Donald Trump” that Cohen “struck me as someone who would be convincing on the witness stand.”

“In my mind, Cohen could be corroborated, and he could be a compelling witness,” Pomerantz wrote. And he said Bragg’s predecessor, for whom Pomerantz worked, came to the same conclusion: “Cy Vance agreed.”

In a court filing opposing Trump’s lawyers’ efforts to bar Cohen from testifying, prosecutors wrote that they “expect Cohen's testimony at trial to be both true and corroborated, including by extensive documentary evidence, the testimony of other witnesses, and defendant’s own statements.”

They described Trump’s lawyers’ suggestion that calling Cohen as witness would induce him to commit perjury as “intentionally inflammatory and totally meritless,” adding: “a witness’s prior false statements are not a basis for precluding that witness from testifying in a new proceeding.”

In fact, it is relatively commonplace for a witness in a criminal case to carry some baggage in the form of legal troubles, although often such witnesses have signed cooperation agreements with the government, which Cohen hasn’t.

In a federal criminal trial in Manhattan in 2018, for example, prosecutors ordered the arrest of one of their own star witnesses while he was testifying. The witness, Todd Howe, had been forced to admit on the witness stand, under cross-examination, that he had committed credit-card fraud after having signed an agreement with the government requiring him to avoid committing future crimes. Howe had already pleaded guilty to eight unrelated felonies, and that night, authorities arrested Howe at his hotel room.

Even so, the jury returned guilty verdicts for two of the four defendants. (The Supreme Court eventually overturned those verdicts for reasons unrelated to Howe’s testimony.)

For Trump, losing the fight to exclude Cohen’s testimony might pale in comparison to the effect of another recent Merchan ruling: a gag order that bars Trump from attacking “reasonably foreseeable witnesses.”

In the pantheon of people who have turned on Trump, perhaps no one has elicited more venom from the former president than Cohen, and now the gag order means Trump can’t, as he did during the civil fraud trial, publicly lambast Cohen as “a proven liar.”

Even with those restrictions, however, Trump hasn’t been able to resist targeting Cohen’s character in the days leading up to the trial. On Saturday, he posted on social media: “Has disgraced attorney and felon Michael Cohen been prosecuted for LYING?”

As for Cohen himself, he dismissed any concerns about his ability to testify truthfully.

“My credibility is predominantly and consistently called into question by Donald and his acolytes,” he wrote to POLITICO in a text message. “Their opinions are of no concern to me because they are inaccurate and self motivated; designed to escape responsibility for his own dirty deeds.”