The source, who Carlson said he would not yet name, said he worked for the brothers' Podesta Group and was privy to some information from Robert Mueller's special investigation.

While media reports describe former "Black, Manafort & Stone" principal Paul Manafort as Trump's main tie to the investigation, the source said it is Manafort's role as a liaison between Russia and the Podesta Group that is drawing the scrutiny.

The "vehicle" Manafort worked for was what Carlson called a "sham" company with a headquarters listed in Belgium but whose contact information was linked to Kiev, the Ukrainian capital.

Manafort was, at the time, representing Russian business and political interests during the Obama era.