Paul Manafort has agreed to cooperate with special counsel Robert Mueller

In a decision that sent shockwaves through Washington’s political circles, President Trump’s former campaign manager, Paul Manafort, agreed to fully cooperate as a potential witness with special counsel Robert Mueller’s Russia probe, the counsel’s office confirmed Friday.

In the sweeping plea agreement, Manafort promised wide-ranging assistance to Mueller’s team, which is investigating whether the Trump campaign collaborated with Russian efforts to influence the 2016 election. The deal includes an agreement to testify in any proceeding requested by investigators, including before a grand jury in Washington DC.

“This is a moment of historic proportions,” Seth Waxman, a former federal prosecutor who now works as a white collar defense attorney, told VICE News. “A member of the inner circle of the campaign is now cooperating with the special counsel. Manafort might hold the keys to the castle.”

Mueller’s team announced they would reduce the charges against Manafort from seven down to two. Shortly thereafter Manafort, 69, pleaded guilty to two charges in a Washington DC court on Friday: conspiracy against the U.S., and conspiracy to obstruct justice.

The plea deal Manafort signed includes broad language, according to a copy of the document released shortly after Manafort appeared in the DC courtroom to enter his guilty plea.

“Your client shall cooperate fully, truthfully, completely, and forthrightly with all the Government and other law enforcement authorities identified by the Government in any and all matters as to which the Government deems the cooperation relevant,” the document says.

“This is a huge moment for Mueller,” Gene Rossi, a former federal prosecutor, told VICE News.

Read: Paul Manafort, a Russian jet and a secret meeting during the 2016 campaign

Manafort’s full cooperation marks a stunning new twist in the wide-ranging Mueller probe, said Waxman, and creates new legal jeopardy for the president himself, and potentially even members of his family.

“This might endanger not only the president, but the president’s family members, including Don Jr. and Jared Kushner, who could now find themselves in the crosshairs of the investigation as a next step,” Waxman said.

Manafort might be able to shed new light on the infamous Trump Tower meeting in June 2016 at the height of the campaign, in which the top brass of the Trump campaign met with a lawyer from Moscow billed as bringing dirt on Trump’s opponent, Hillary Clinton, Waxman said. Manafort participated in that meeting along with Trump’s son Don Jr. and son-in-law Jared Kushner.

The White House quickly tried to mute the impact of the deal, and create more distance between the president and his former campaign chairman.

“This had absolutely nothing to do with the President or his victorious 2016 Presidential campaign,” White House press secretary Sarah Huckabee Sanders said in reaction to the announcement. “It is totally unrelated.”

Read: Paul Manafort just cut a deal with Mueller and will plead guilty

But that’s not how legal experts see it. Most agreed with Waxman’s view that Manafort’s cooperation deal opened up a vast new chasm of legal peril for Trump’s inner circle.

“This is potentially devastating for Trump and other members of his campaign,” said Mimi Rocah, a former federal prosecutor.

“Manafort will almost certainly have to cooperate about everything and everyone,” she said. “They would not sign him up to cooperate against just himself.”

“The clear inference here is that they’re signing him up to get people who were involved the campaign, in which Manafort played a key role,” Rocah said. “That’s clearly the way this is headed.”

Manafort had already been found guilty on eight counts of bank and tax fraud in an earlier trial in Alexandria, Virginia. In Washington, he had initially faced a second round of charges for allegedly failing to register as an agent of a foreign government, making false statements, obstruction of justice and conspiracy to launder money.

But a new superseding indictment announced Friday morning lumped those claims together under the new, reduced charges while listing many of the same detailed allegations, plus some new ones, in the 38-page document.

The indictment says Manafort laundered more than $30 million and “cheated the United States out of over $15 million in taxes” while working as an advisor to the former President of Ukraine, Viktor Yanukovych.

According to court documents, Manafort, by pleading guilty, agreed to forfeit four homes and multiple bank accounts. He also agreed to plead guilty to the ten counts that the jury in Virginia couldn’t reach an agreement on, and promised not to appeal.

Upon exiting the courtroom, Manafort’s lawyer, Kevin Downing, told reporters that Manafort’s decision had been influenced by concern for his family.

“He wanted to make sure that his family was able to remain safe and live a good life,” Downing said. “He’s accepted responsibility, and this is for conduct that dates back many years, and everyone should remember that.”

“Tough day for Mr. Manafort,” Downing said.

Cover image: Former Trump campaign manager Paul Manafort departs from U.S. District Court in Washington, U.S., February 28, 2018. REUTERS/Yuri Gripas