Friday morning, former Trump 2016 campaign chairman Paul Manafort appeared in a Washington, D.C. federal court and pleaded guilty to one count of conspiracy against the United States and conspiracy to obstruct justice. Manafort has also agreed to cooperate fully with Special Counsel Robert Mueller in exchange for leniency when he’s sentenced.

Later in the day, White House Press Secretary Sarah Sanders had this to say about Manafort’s plea agreement:

“This had absolutely nothing to do with the President or his victorious 2016 Presidential campaign. It is totally unrelated.”

But legal experts could not possibly disagree more. They say that the Manafort deal — and his agreement to fully cooperate with the special counsel — is the worst news possible for Donald Trump.

Jed Shugerman, a law professor at Fordham University, told Vox:

“Does Manafort have information that Trump knew about the (2016 Trump Tower) meeting in advance? I’ve written before that such advance knowledge would be the key step in establishing felony conspiracy against the United States.”

Andy Wright, the founding editor of the legal blog Just Security, said news of Manafort’s plea agreement should be of special concern to Trump, and even the president has said so:

“It is clear that President Trump is concerned about what Manafort might say. The president has reportedly told associates Manafort could incriminate him. And he has publicly celebrated Manafort’s previous omertà throughout Manafort’s criminal proceedings. Manafort’s plea will cap his imprisonment for these charges at 10 years, and he will get the benefit of a significant reduction if he provides robust and truthful cooperation.”

And Miriam Baer, who serves as a law professor at Vanderbilt University, noted that Manafort’s willingness to cooperate with Mueller could also encourage others to tell Mueller what they know about the Russia conspiracy:

“Those who committed crimes in concert with Manafort are now on notice that a co-conspirator has decided to ‘spill the beans.’ Accordingly, Manafort’s cooperation agreement may well induce other targets to come forward with evidence and seek the benefits of a cooperation agreement.”

Mueller now has Donald Trump in legal checkmate from which there is no escape. Trump can either resign or face the coming indictments and impeachment that await him. He’s out of cards to play that will extricate him from the self-created hell that’s headed his way.