Washington (CNN) Special counsel Robert Mueller believes that Paul Manafort was sharing polling data and discussing Russian-Ukrainian policy with his close Russian-intelligence-linked associate, Konstantin Kilimnik, while he led the Trump presidential campaign, according to parts of a court filing that were meant to be redacted by Manafort's legal team Tuesday but were released publicly.

Manafort discussed a Ukrainian peace plan with Kilimnik, his lawyers acknowledged. He also shared polling data related to the 2016 presidential campaign with Kilimnik, Manafort's legal team acknowledges in their court filing.

The details accidentally released Tuesday are the closest public assertion yet in the Mueller cases of coordination between a Trump campaign official and the Russian government, as Kilimnik is believed to be linked to Russian military intelligence. It's a major acknowledgment from the Mueller team that their investigation into Russian interference in the 2016 election is finding potential contact between at least one Trump campaign official and the Kremlin.

The Ukraine peace plan that they discussed likely would have dealt with Russian intervention in the region. At around the same time, Russian government operatives were allegedly hacking Democratic computers to help Trump and orchestrating a social media propaganda scheme to sway voters against Trump's electoral opponents.

Kilimnik has long been suspected to be central to Mueller's investigation into Russian influence in the 2016 presidential election. The revelations in the court filing Tuesday seem to confirm that.

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