Manafort on Friday pleaded guilty to one count of conspiracy against the and one count of conspiracy to obstruct justice brought by Mueller's team. "He did so knowingly, intentionally and willfully", Weissmann said.
Manafort's cooperation in this investigation has eliminated a potential 10-year prison sentence.
His flip means five key players from Trump's inner circle have now been convicted, pleaded guilty or agreed to immunity deals in exchange for talking to prosecutors. Manafort's plea makes reference to a written proffer agreement on Tuesday - showing he has been in talks with the special counsel's office at least for several days. "Specifically, Manafort conspired to act and acted as an agent of the Government of Ukraine, the Party of Regions (a Ukrainian political party whose leader Victor Yanukovych was President from 2010 to 2014), President Yanukovych, and the Opposition Bloc (a successor to the Party of Regions that formed in 2014 when Yanukovych fled to Russia)", the court document reads.
"The decision by Manafort to provide evidence in exchange for leniency on sentencing is a stunning development in the long-running probe into whether any Trump associates may have conspired with Russian Federation to influence the 2016 election", reported The Washington Post.
When Paul Manafort was first charged by prosecutors past year, court documents read like the opening scene of lives of the rich and famous: From multiple properties complete with gardens manicured in the form of an "M" for the GOP operative's name to high-priced shopping sprees to custom-made suits.
But Harvard law professor emeritus Alan Dershowitz said Giuliani is putting a positive spin on "bad" situation for President Trump.
Now, however, Trump's comments may no longer be "operative", as White House officials might have said in another time and place. Manafort was found guilty on eight charges, including tax fraud by a Virginia court last month.
- He has information about Trump himself.
In August, after Cohen pleaded guilty, Trump praised Manafort for refusing to "break", suggesting that Manafort holding strong was very much in his interest.
White House press secretary Sarah Huckabee Sanders issued a brief statement after the announcement.
- He has information about what happened in the Trump campaign, but that information doesn't touch the president directly. And when he worked on the campaign, emails show Mr Manafort discussed providing private briefings for a Russian businessman close to Vladimir Putin.
That could be potentially damaging for Donald Trump and his eldest son, Donald Trump Jr., as Manafort was present at the Trump Tower meeting in 2016 where members of the campaign met with a Kremlin-connected lawyer promising dirt on Hillary Clinton.
The president Tuesday called the outcome a "disgrace" and said the case "has nothing to do with Russian Federation collusion".
"I understand why Rudy Giuliani, who's a good lawyer, wants to put this in the most positive light, but this was a very bad day for the Trump administration", Dershowitz continued.
FILE - Former Trump campaign manager Paul Manafort arrives for arraignment on charges of witness tampering, at U.S. District Court in Washington, June 15, 2018.
Even if Manafort has helped Trump and Republicans, in one sense, by vitiating a high-profile trial this fall, he may hurt them politically - or, ultimately, legally - by cooperating with the Justice Department.
"I did. It is", Manafort said, resting both hands on the lectern before him and flanked by his attorney Richard Westling. He faces roughly 10 years in the Washington case and perhaps another 10 in Virginia - though he would probably be able to serve those together, particularly if prosecutors urge judges to go easy on him. Manafort pleaded guilty to those charges.