Manafort’s plea could be a key cog in pushing Mueller’s case toward its ultimate end. Legal analysts say Manafort must have something valuable to share with Mueller’s team, which agreed to drop five of the seven charges he faced and potentially urge leniency at his sentencing, if his cooperation is helpful.

Generally, those who plead guilty sit down with prosecutors to detail what they know in a “proffer” session, so the government knows what it will get in the bargain. 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.

Whether Manafort ultimately implicates the president remains to be seen. Manafort’s defenders and Trump’s lawyers have long insisted that the political consultant, who left the campaign in August 2016, had no information that would incriminate Trump.

“I think Robert Mueller’s real quest here is for the truth, and Paul Manafort can get him closer to knowing the truth,” former U.S. attorney Barbara McQuade said.