Former Trump campaign chairman Paul Manafort shared polling data during the 2016 presidential campaign with a business associate accused of having ties to Russian intelligence, and prosecutors say he lied to them about it, according to a court filing.
The allegation marks the first time prosecutors have accused Mr Trump's chief campaign aide of sharing information related to the election with his Russian contacts.
Although the filing does not say whether the polling information was public or what was done with it, it raises the possibility that Russia might have used inside information from Mr Trump's Republican campaign as part of its effort to interfere with the election on Mr Trump's behalf.
The information was accidentally revealed in a defence filing that was meant to be redacted.
The Associated Press was able to review the material because it was not properly blacked out.
What does the filing say?
The filing revealed the first extensive details of what Manfort is accused of having lied about.
The filing contains new details about his connection to Konstantin Kilimnik, a Russian-Ukrainian business associate who was indicted last year on charges he tampered with potential witnesses.
The US believes he is connected to Russian intelligence, but Mr Kilimnik, who is not in US custody, has denied those ties.
The latest allegations further detail how Manafort's work on the campaign intersected with his past international work with Mr Kilimnik.
Emails previously reported by news outlets show that in July 2016, Manafort told Mr Kilimnik he was willing to provide "private briefings" about the Trump campaign to Oleg Deripaska, a Russian billionaire with ties to Russian President Vladimir Putin.
Manafort dangled the briefings as he was mired in a dispute with Mr Deripaska over a multi-million-dollar deal involving a Ukrainian cable company.
Through his spokesman, Manafort has acknowledged discussing the briefings, but said they never occurred.
The defence document acknowledges Manafort conceded he had met with Mr Kilimnik in Madrid only after being told that they had travelled to the city on the same day.
Manafort spokesman Jason Maloni said the Madrid trip mentioned in the filing occurred in January or February 2017 — months after Manafort was ousted from the campaign and as Mr Trump was taking office.
What's the background on Manafort?
Manafort was among the first Americans charged in special counsel Robert Mueller's investigation and has been among the central characters in the case.
He led the Trump campaign during the Republican convention when, US intelligence officials say, Russia was working to sway the election in Mr Trump's favour.
Manafort has pleaded guilty to conspiracy charges in Washington and faces sentencing in a separate case in Virginia.
In its filing on Tuesday (local time) the defence was trying to rebut allegations Manafort intentionally lied to Mr Mueller's team after agreeing to plead guilty last September.
Prosecutors say Manafort breached their plea agreement by lying, but defence lawyers argue that any misstatements were simple mistakes made by a man coping with illness, exhaustion and extensive questioning from investigators.
Lawyers say Manafort suffers from depression and anxiety, has had little contact with his family and, on days when he met with investigators, was awakened before dawn to have hours-long interviews with little time to prepare for the questioning.
"These circumstances weighed heavily on Mr Manafort's state of mind and on his memory as he was questioned at length," the lawyers wrote.
What's going to happen next?
Prosecutors have also accused Manafort of lying about his contacts with Trump administration officials, which defence lawyers also deny.
The filing says a May 26, 2018, text message exchange with Manafort involved an unidentified "third party" who was asking permission to name-drop Manafort if the person met with Mr Trump.
The request to use Manafort as an introduction to Mr Trump came while Manafort was under indictment in two federal cases.
The defence team says Mr Mueller's team has indicated it will not pursue additional charges against Manafort.
Defence lawyers say they don't want a separate hearing before a judge on the lying allegations, but will address them instead during the sentencing process.
