It remains to be seen whether Manafort has any evidence to offer Mueller even were he to cooperate. Manafort’s allies have said repeatedly that he has no proof of collusion between Russia and President Donald Trump’s campaign, and that he has no intention of aiding the government.

“There is no evidence that Mr. Manafort or the Trump campaign colluded with the Russian government," Downing said.

And Manafort may still hold out hope that Trump will eventually pardon him. Trump’s press secretary Sarah Sanders said Monday the issue of a pardon hasn’t been discussed.

Talks Unsuccessful

The indictment of Manafort and Gates by a grand jury suggests negotiations between Mueller and the defense teams were unsuccessful -- if they occurred at all.

“Generally, the earlier you negotiate an agreement, the more favorable the terms,” said Samuel W. Buell, a law professor at Duke law school in Durham, North Carolina.

Prosecutors can also file additional, and more aggressive, charges later, such as tax evasion over the alleged failure to disclose foreign income to the Internal Revenue Service. But it may not be necessary to do so since the existing indictment already presents a substantial threat to Manafort and Gates, according to experts.

For years, Manafort and Gates represented  Victor Yanukovych’s pro-Russian regime in Ukraine. They led a lobbying campaign in the U.S. from 2012 to 2014 to advance their clients’ interests, pressing members of Congress about U.S.-imposed sanctions related to Ukraine, the validity of the country’s elections and the propriety of the jailing of Yanukovych’s rival in the presidential election. They paid lobbyists $2 million from undisclosed foreign accounts, and another $4 million to produce a report about Yanukovych’s rival, according to prosecutors.

Shell Companies

Manafort is accused of laundering $18 million through the U.S. financial system using a web of foreign shell companies and bank accounts, while Gates is alleged to have laundered $3 million. Manafort and Gates had foreign accounts linked to 15 shell companies in Cyprus, the Grenadines, the Seychelles and the U.K. that should have been disclosed, prosecutors said. The two are also accused of using the foreign accounts to pay for luxury goods, homes and personal expenses in the U.S. without declaring the income.