Mueller's office released unsealed court records on Monday showing Papadopoulos admitted to misleading FBI agents during interviews on Jan. 27 and Feb. 17 about his contact with people thought to be connected to high-ranking Russian officials.
The case marks the first known guilty plea connected to the Mueller investigation.
Papadopoulos told investigators that he understood that one of the Trump campaign's main foreign policy goals was to improve relations between Washington and Moscow. To that end, he tried several times to set up meetings between Trump campaign and Russian government officials.
He failed to disclose his attempts to authorities, despite inquiries from the FBI.
He admitted that he lied about when he met a London-based professor who claimed that the Russians had "thousands of emails" that amounted to "dirt" on Trump rival Hillary Clinton. He told that he met the professor before joining the presidential campaign in March 2016 and attempted to downplay their communications, telling agents that he believed the professor "was 'BS'ing, to be completely honest."
However, officials determined that the meeting took place in London days after Papadopoulos joined the Trump campaign and that Papadopoulos kept contact with the professor for months. He believed the professor was well-connected in Russian government circles and communicated with him about foreign policy issues in an effort to arrange a “history making” meeting between Trump campaign and Russian government officials, court records show.
He also lied about his contact with an unnamed Russia woman, who he identified in an email as “(Russian President Vladimir) Putin’s niece,” and contact with a person who said he had connections to the Russian Ministry of Foreign Affairs, court records show.
Authorities said Papadopoulos believed the unidentified Russian woman could help him to arrange a possible foreign policy trip to Russia.
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Officials indicated that Papadopoulos made moves to bury his ties to the professor and the person connected to the Russian Foreign Ministry when, one day after his second interview with FBI officials, he deactivated a longtime Facebook account that he kept "which contained information about communications he had with the Professor and the Russian MFA Connection," authorities said. He created a new Facebook page a short time later, which did not have the information on it.
Papadopoulos also switched to a new phone number that same month.
Authorities arrested Papadopoulos at Washington Dulles International Airport on July 27 and has since agreed to cooperate with investigators, according to court records.
Mueller’s investigation continues.
Two other Trump campaign advisers, former campaign manager Paul Manafort and his associate Rick Gates, were indicted on a slew of charges Friday, including accusations that they conspired against the United States. Both men turned themselves in to authorities Monday.