Manafort's cooperation with Mueller could provide investigators new evidence or leads to chase; a guilty plea, however, would prevent weeks' worth of headlines about the trial in the month before congressional elections.
"I feel very badly for Paul Manafort and his wonderful family", the President tweeted the week of Manafort's conviction in his Virginia trial.
Manafort, wearing a dark suit, white shirt and purple tie, appeared upbeat as he arrived in court where he quickly took his place at the podium to enter his plea of guilty to two conspiracy counts, including conspiracy to obstruct justice.
Manafort made millions of dollars working for pro-Russian Ukrainian politicians before taking an unpaid position with Trump's campaign for five months.
In pleading guilty, Manafort, the former Trump campaign chairman, would admit he broke the law - a concession he refused to make throughout his Alexandria trial and since he was charged almost a year ago in Washington. Now that trial is canceled.More news: Is everything fine in the White House?
The plea, and cooperation, were an abrupt change for Manafort, who was convicted last month in the Virginia federal court on bank and tax fraud charges.
As we know, Mueller has indicted 25 Russians (13 Russian entities were indicted earlier this year for their propaganda campaign, and 12 Russian intelligence officers (GRU) were indicted for hacking the DNC, DCCC, and Hillary Clinton's presidential campaign during the 2016 election and leaking through DCLeaks and Guccifer 2.0).
The White House says Manafort's decision to plead guilty and cooperate with Mueller is "totally unrelated" to President Donald Trump. Trump's lawyer, Rudy Giuliani, had suggested a pardon might be a possibility after the investigation was concluded. The reason: "the President did nothing wrong".
They were charged in connection with their work for Ukrainian political parties and pro-Russian former president Viktor Yanukovych.
Rudy Giuliani, the former New York City mayor who is now representing Trump in the Russian Federation probe, told Reuters news agency on Friday that a guilty plea to avoid a second trial would not crush Manafort's chances of receiving an eventual presidential pardon.
Manafort is shown at the Republican convention in Cleveland behind Donald Trump on July 21, 2016.More news: Amazon CEO Jeff Bezos launches a $2 bln philanthropic fund
But what Manafort knows about the Trump Tower Russian meeting may be only "the tip of the iceberg", according to Vox's worldwide security expert Alex Ward. Usually it helps you get a pardon down the road.
On Friday, prosecutor Andrew Weissman said in court that Manafort had struck a "co-operation agreement" and would plead guilty to charges related to his Ukrainian political consulting work. For now, Manafort has agreed to cough up close to $50 million to the feds in penalties, enough, incidentally, to pay for the Mueller investigation's activities for several years. Mueller has also gotten guilty pleas from former national security adviser Michael Flynn and former foreign policy adviser George Papadopoulos.
That case alleged that Manafort directed a large-scale USA lobbying operation for Ukrainian interests but never registered with the Justice Department as a foreign agent despite being required to do so under the law, and that he concealed millions of dollars in income for the consulting work from the IRS.
Legal experts characterized Manafort's move as a significant win for Mueller-and a big setback for Trump.
The charges in the information say that Manafort will have to forfeit property that was derived from or traceable to his offenses.
Asked by Kornacki if this is really all about Trump, Dershowitz said, "There's no doubt about that".More news: Trump made false claim about economy, GDP, unemployment rate: White House
Neither of the cases against Manafort relates to Russian interference in the 2016 presidential election, the central issue in the special counsel's investigation.