Former Trump campaign aide Sam Nunberg revealed in a recent interview that he believes special counsel Robert Mueller’s investigators “have a strong case of a conspiracy” involving Russia.

Nunberg made the assertion while speaking to John Heilemann on Showtime’s The Circus program.

“When I went to the special counsel for the voluntary interview, it was, ‘Roger, Roger Roger, Roger,'” Nunberg said, referring to Trump confidante Roger Stone.

Nunberg said that prosecutors wanted to know “what did Roger and Trump discuss in their phone calls.”

“I could tell what they were going to do to Roger,” he explained. “I think Roger could tell what they’re going to do to Trump. These aren’t the guys you fuck around with. They have a strong case of a conspiracy.”

Nunberg said that he didn’t believe that President Donald Trump personally spoke to Russian President Vladimir Putin during the 2016 campaign.

“But what I do know is that there’s something going on there,” he added. “There’s a lot of stuff to look into.”

Watch the video above from Showtime.