Former Trump aide Paul Manafort has agreed to cooperate with investigators – what might he know?

As Trump associates folded one-by-one over the last year under the pressure of federal investigators, there was always Paul Manafort. Until suddenly there wasn’t.

The former Trump campaign chairman, who for months stood resolute in his innocence and determined to fight charge upon charge even as fellow one-time loyalists caved, reached an extraordinary plea agreement with special counsel Robert Mueller’s office on Friday that requires him to assist the Russia investigation and converts him into a potentially vital government cooperator.

The deal, struck in Washington just days before Manafort was to have faced a second trial, is tied to Ukrainian political consulting work and unrelated to the Trump campaign. But the key question remains what information Manafort, 69, is able to provide about the president and the question of whether the Trump election effort coordinated with Russia.

His leadership of the campaign at a time when prosecutors say Russian intelligence was working to sway the election, and his involvement in episodes under scrutiny, may make him an especially insightful witness

He was among the participants in a June 2016 Trump Tower meeting with Russians and Trump’s oldest son and son-in-law that was arranged for the campaign to receive derogatory information about Democrat Hillary Clinton.

He was also a close business associate of a man who US intelligence believes has ties to Russian intelligence. And while he was working on the campaign, emails show Manafort discussed providing private briefings for a wealthy Russian businessman close to Vladimir Putin.

“The expectations around Manafort’s cooperation are likely at a level beyond anyone else to date who has agreed to cooperate,” said Jacob Frenkel, a Washington lawyer not involved in the case. “Whether those expectations will be met is the great unknown.”