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The Russia investigation cannot be dismissed by the White House as "fake news," Judge Andrew Napolitano explained.

The Fox News senior judicial analyst emphasized the seriousness of the guilty plea by former Trump campaign foreign policy adviser George Papadopoulos, who he said most likely "wore a wire" to potentially gather incriminating evidence against other Trump campaign officials.

Special Counsel Robert Mueller announced the guilty plea on Monday, saying Papadopoulos lied to FBI agents about contacts with a Russia-linked professor who spoke of "dirt" on Hillary Clinton in the spring of 2016.

The professor, based in London, has denied the claims laid out by Papadopoulos. Napolitano said the guilty plea by Papadopoulos was "very unusual" because it occurred in secret and the judge ordered the plea documents to be sealed.

Napolitano said for that to happen, prosecutors would need to convince the court that a lack of secrecy would "materially interfere with an ongoing criminal investigation."

He explained that the judge's decision was likely based on Papadopoulos "wearing a wire" as a cooperating witness.

Napolitano also said it's telling that Papadopoulos was not charged with obstruction of justice, perhaps because he has already provided "significant assistance" to investigators.

Napolitano said Papadopoulos could end up getting off with just probation depending on how much information he provides to Mueller's team.

The judge said the charges unveiled against former Trump campaign manager Paul Manafort and his associate, Rick Gates, are enough to put both in jail for the rest of their lives.

"That will cause their lawyers to start negotiating with Bob Mueller," he predicted.

Watch more above.

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