WASHINGTON • As a top official in United States President Donald Trump's campaign team, Paul Manafort shared political polling data with a business associate tied to Russian intelligence, according to a court filing unsealed on Tuesday.
The document provided the clearest evidence to date that the Trump campaign may have tried to coordinate with Russians during the 2016 presidential race.
Manafort's lawyers made the disclosure by accident, through a formatting error in a document filed to respond to charges that he had lied to prosecutors working for the special counsel, Mr Robert Mueller, after agreeing to cooperate with their investigation into Russian interference in the election.
The document also revealed that during the campaign, Manafort and his Russian associate, Mr Konstantin Kilimnik, discussed a plan for peace in Ukraine.
Throughout the campaign and the early days of the Trump administration, Russia and its allies were pushing various plans for Ukraine, in the hope of gaining relief from US-led sanctions imposed after it annexed Crimea from Ukraine.
Prosecutors and the news media have documented a string of encounters between Russian operatives and Trump campaign associates dating from the early months of Mr Trump's bid for the presidency, including the now-famous meeting at Trump Tower in Manhattan with a Russian lawyer promising damaging information on Democratic nominee Hilary Clinton.
The accidental disclosure appeared to some experts to be perhaps most damning of all.
"This is the closest thing we have seen to collusion," Mr Clint Watts, a senior fellow with the Foreign Policy Research Institute, said of the data-sharing. "The question now is, did the President know about it?"
From March to August 2016, when Manafort worked for the Trump campaign, Russia was engaged in a full-fledged operation using social media, stolen e-mails and other tactics to boost Mr Trump, attack Mrs Clinton and play on divisive issues such as race and guns.
Polling data could conceivably have helped Russia hone those messages and target audiences to help swing votes to Mr Trump.
Both Manafort and deputy campaign manager Rick Gates transferred the data to Mr Kilimnik in the spring of 2016 as Mr Trump clinched the Republican presidential nomination, said a source.
Some of the data was developed by a private polling firm working for the campaign, the source said.
Manafort asked Gates to tell Mr Kilimnik to pass the data to Mr Oleg Deripaska, a Russian oligarch who is close to the Kremlin and who has claimed that Manafort owed him money from a failed business venture, the source added.
It is unclear whether Manafort was acting at the campaign's behest or independently, trying to gain favour with someone to whom he was deeply in debt.
Manafort, 69, has been in jail in Northern Virginia since mid-June. One prosecution resulted in his jury conviction in August for bank fraud, tax fraud and other financial crimes. A second led to his guilty plea in September on two conspiracy charges, including one stemming from a witness-tampering scheme with Mr Kilimnik. Manafort faces at least 10 years in prison.