On the other side, a possible point of contact might be Konstantin Kilimnik, who the FBI believes has ties to Russian intelligence. A former employee of Manafort’s firm, Kilimnik was sometimes described as “Manafort’s Manafort,” while Manafort reportedly called him “my Russian brain.” A poorly redacted court filing from Mueller’s team inadvertently revealed that Manafort gave Kilimnik detailed polling information during the campaign and discussed a Ukrainian peace plan, then lied about both to Mueller, even when he was supposedly cooperating. Mueller charged Kilimnik with conspiracy to obstruct justice and obstruction of justice for allegedly attempting witness tampering during the Manafort investigation.

Using multicolored flow charts in an attempt to simplify complex transactions, prosecutors tried to show that Mr. Manafort concealed more than $60 million in income in 31 foreign bank accounts opened in the names of shell companies.

The money came from Ukrainian oligarchs who paid Mr. Manafort to boost the political career of Viktor F. Yanukovych, a pro-Russian politician who, with Mr. Manafort’s help was elected president of Ukraine in 2010.