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Former Trump campaign chairman Paul Manafort was wiretapped by U.S. government investigators both before and after the 2016 presidential election, according to a new report.

Manafort is a key figure in Special Counsel Robert Mueller’s investigation into Russia’s involvement with the election.

On "Fox & Friends," Judge Andrew Napolitano explained that the FBI obtained a warrant from a FISA court to surveil Manafort in 2014 because of his work with the pro-Russia political party in Ukraine. That warrant was discontinued, but investigators received another one that extended into the beginning of this year.

He said it's not clear if this new one is a FISA or a regular Article III judge warrant, which he said is a "real serious distinction."

He explained that to obtain the latter, investigators would have to present a federal judge with evidence of crimes committed by Manafort or the people he was speaking to.

"Were they listening to Paul Manafort during the campaign in order to find out what Donald Trump was going to do next in the campaign and help Hillary? Were they listening to Paul Manafort because they thought he had committed a crime? Were they listening to Paul Manafort because they were looking for something with which to tarnish the future president?" Napolitano said.

"I think there's more to be heard."

Watch more above.

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