All Paul Manafort had to do to keep his plea deal with special counsel Robert Mueller is tell the truth. According to a new court filing, however, the former campaign manager allegedly lied repeatedly to Mueller’s investigators. If accepted by the court, the allegation makes Manafort liable for a very long stretch in prison — but Manafort’s not the only one with a problem:

Prosecutors with special counsel Robert S. Mueller III said Monday that Paul Manafort breached his plea agreement, accusing President Trump’s former campaign chairman of lying repeatedly to them in their investigation into Russian interference in the 2016 election.

Manafort denied doing so intentionally, but both sides agreed in a court filing that U.S. District Judge Amy Berman Jackson of the District should set sentencing immediately.

The apparent collapse of Manafort’s cooperation agreement is the latest stunning turnaround in his case, exposing the longtime Republican consultant to at least a decade behind bars after he pleaded guilty in September to charges of cheating the Internal Revenue Service, violating foreign-lobbying laws and attempting to obstruct justice.

So what did Manafort lie about? The filing accuses him of multiple falsehoods, but doesn’t get specific. Mueller’s office promises to elaborate later when preparing for the sentencing hearing:

“After signing the plea agreement, Manafort committed federal crimes by lying to the Federal Bureau of Investigation and the Special Counsel’s Office on a variety of subject matters, which constitute breaches of the agreement,” prosecutors wrote. “The government will file a detailed sentencing submission to the Probation Department and the Court in advance of sentencing that sets forth the nature of the defendant’s crimes and lies.”

The deal may be off, but only as it applies to sentencing. The terms of the plea agreement waive any right to retract Manafort’s guilty pleas, so he’s on the hook no matter what. Manafort’s legal team will have to convince Judge Berman Jackson that Manafort offered an honest effort to comply with Mueller’s team just to get a sentence within the original deal’s parameters, which is now their best-case scenario.

So Manafort has a lot more headaches now, but then again, so does Mueller. The New York Times explains the implications for Mueller’s investigation in calling their biggest potential witness a liar:

“Everybody who lies to Mueller gets called on it — so he had to know that Mueller would catch him. So the question is: What was he hiding that is worse than going to jail for the rest of your life?” said Joyce Vance, a professor of law at the University of Alabama law school and former federal prosecutor. “There are often rocky dealings with a cooperator, and Mueller didn’t cut bait at the first sign of trouble. It was likely more than one lie and this would not have been a minor detail — it had to be something material and significant and intentional.” …

The filing Monday suggested that prosecutors do not consider Mr. Manafort a credible witness. Even if he has provided information that helps them develop criminal cases, by asserting that he repeatedly lied, they could hardly call him to testify.

And that’s the headache. The theories of Russian collusion with the Trump campaign have to run through Paul Manafort in order to make any sense. He’s the only person in the campaign (however briefly) with both substantial connections to Moscow and a close enough link to Trump to matter. If there was collusion between the Trump campaign and Russian operatives (a hypothesis without any evidence in support thus far), Manafort would either have to have been part of it or known of it.

That led to the plea deal itself. Mueller’s intent on picking the Department of Justice’s old money-laundering and FARA cases was obviously to force Manafort to turn on Trump and testify against him on this point. In fact, it was so obvious that Judge T. S. Ellis threatened to throw out all charges against Manafort back in May over the special counsel’s role in prosecuting these specific charges. Ellis let the case go forward, but Mueller’s motives were plain.

Now, however, Manafort’s useless as a witness to Mueller. The special counsel has done a lot of work for nothing — or at best, nothing the DoJ couldn’t have accomplished on its own regarding Manafort and his ex-partner Rick Gates. Not only have they demolished Manafort’s standing as a witness, by calling Manafort a liar they have poisoned any information the special counsel has developed through his earlier cooperation. Nothing produced from Manafort would have credibility in court, which makes Manafort a big empty hole in the middle of any realistic collusion hypothesis.

Manafort will likely spend the rest of his life in prison now. Mueller may well spend the rest of his career as special counsel spinning his wheels.