Manafort plea deal begs key question: What does he know?

This courtroom sketch depicts former Donald Trump campaign chairman Paul Manafort, center, and his defense lawyer Richard Westling, left, before U.S.

This courtroom sketch depicts former Donald Trump campaign chairman Paul Manafort, center, and his defense lawyer Richard Westling, left, before U.S.

FILE - In this Feb. 14, 2018 file photo, Paul Manafort, President Donald Trump's former campaign chairman, leaves the federal courthouse in Washington

FILE - In this Feb. 14, 2018 file photo, Paul Manafort, President Donald Trump's former campaign chairman, leaves the federal courthouse in Washington

Paul Manafort's wife Kathleen Manafort, left, arrives at federal court in Washington, Friday, Sept. 14, 2018. Former Trump campaign chairman Paul Mana

Paul Manafort's wife Kathleen Manafort, left, arrives at federal court in Washington, Friday, Sept. 14, 2018. Former Trump campaign chairman Paul Mana

Members of the media follow attorney Kevin Downing, center, with the defense team for Paul Manafort, leaving federal court in Washington, Friday, Sept

Members of the media follow attorney Kevin Downing, center, with the defense team for Paul Manafort, leaving federal court in Washington, Friday, Sept

Attorney Kevin Downing, center, with the defense team for Paul Manafort, watches as television cameraman Chris Plater, trips and falls backwards outsi

Attorney Kevin Downing, center, with the defense team for Paul Manafort, watches as television cameraman Chris Plater, trips and falls backwards outsi

WASHINGTON (AP) — Paul Manafort stood resolute as Trump associates folded one-by-one over the last year under the pressure of federal investigators.

But that finally changed.

The former Trump campaign chairman, who for months was determined to fight charge upon charge even as fellow onetime loyalists caved, reached an extraordinary plea agreement with special counsel Robert Mueller's office on Friday. It 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 question of whether the Trump election effort coordinated with Russia.