President Trump’s former campaign chief, Paul Manafort, pleaded guilty Friday and agreed to cooperate with Special Counsel Robert Mueller, who is investigating Russian interference in the 2016 election.

He will also forfeit tens of millions in cash and property, including a Brooklyn brownstone, a Hamptons estate–and his 43rd floor apartment in Trump Tower, court documents show.

Wearing a loose-fitting suit, Manafort pleaded guilty to one count of conspiracy against the United States and one count of obstruction in connection while admitting to a wide range of illegal behavior detailed in a superseding criminal information.

As part of the deal, he agrees to sit for interviews with Mueller's prosecutors and turn over documents. He won't be sentenced until his cooperation ends, at which point Mueller can decide whether to recommend a lower sentences.

"It’s a tough day for Mr. Manafort, but he’s accepted responsibility," his attorney, Kevin Downing said outside court. "He wanted to make sure that his family was able to remain safe and live a good life."

Downing said the plea covered "conduct that went back many years," and the White House also seized on the fact that Manafort has not been charged with any crimes linked to election meddling.

"This had absolutely nothing to do with the president or his victorious 2016 presidential campaign," White House Press Secretary Sarah Sanders said. "It is totally unrelated."

Trump has expressed sympathy for Manafort as he's fought charges brought by Mueller for a year. It's not clear how Manafort's decision to flip could affect any chance of winning a pardon from the president.

Manafort worked for the campaign for five months and attended a Trump Tower meeting with Russians that has drawn Mueller's scrutiny. He and his business partner, Rick Gates, were indicted in May 17.

Gates copped a plea and testified against Mueller at a federal fraud trial in Alexandria, Virginia, where the jury convicted him of eight counts but deadlocked on 10 other counts. Prosecutors agreed to dismiss those 10 counts as part of the deal.

He is the sixth person to cut a deal with Mueller, who previously secured guilty pleas from Gates, former Trump National Security Adviser Mike Flynn, former campaign aide George Papadopoulos, and Dutch attorney Alex van der Zwaan. In addition, Trump's former personal attorney, Michael Cohen, pleaded guilty in a Manhattan case that grew out of a referral from Mueller's probe.

None of them faced charges directly related to Mueller's main mission: investigating Russian interference in the 2016 election and possible collusion by the Trump campaign. But Mueller has also gotten indictments against two dozen Russian nationals and entities, including intelligence officers, for meddling in the election. A man who sold bank account numbers to the Russians also pleaded guilty.

ABC News reported on Sept. 12 that Manafort’s attorneys had been discussing a potential deal with Mueller’s team for several weeks. Sources told ABC that Mueller wanted Manafort to share information about Trump as part of a cooperation agreement but Manafort didn’t want to make such a deal.

Rudy Giuliani, the president’s personal lawyer, told Politico that the possibility of a deal didn’t concern him.

“There’s no fear that Paul Manafort would cooperate against the president because there’s nothing to cooperate about and we long ago evaluated him as an honorable man,” he said.

Giuliani also told Politico that Trump and Manafort’s attorneys have been sharing information throughout the investigation through a joint defense agreement.

After working for a host of Republican politicians, Manafort lobbied for a host of foreign authoritarians and strongmen, including Ferdinand Marcos, Mobutu Sese Seko, Sani Abacha, and Jonas Savimbi. Those men have drawn criticism from human rights watchdogs for a host of bad actions, including embezzling billions of dollars, torturing people in prison, and recruiting child soldiers.

Manafort’s work for Viktor Yanukovych, the Russia-friendly former president of Ukraine, has drawn Mueller’s attention. Mueller’s prosecutors allege that Manafort illegally lobbied in the United States on behalf of Yanukovych and his political party. The charges sent shockwaves through Washington’s clubby lobbying community, where many influence-dealers are unaccustomed to muscular federal enforcement of lobbying laws.