Accorfing to other sites providing more detailed information on the cyber-security committe hearings:

"In the latest change of the narrative, this time the allegation is that Russia provided the hacked data through a third party, three U.S. officials said on Wednesday.... In keeping with the theme of providing no proof to the general public, the officials declined to describe the intelligence obtained about the involvement of a third-party in passing on leaked material to WikiLeaks, saying they did not want to reveal how the U.S. government had obtained the information. So just trust them, please."

Today's Senate committee meetings will focus on cyber-security because, as everyone not already on the "blame Russia" train knows, the real cause of the problem was non-existent cybersecurity measures on the DNC servers and John Podesta's private gmail account. 

Both of these are private, non-governmentalentities, and reflect badly on their competence and professionaliam.