( CNN) Democrats on the House Intelligence Committee thought they had scored a takeover in their efforts to continue investigating Russian interference in the 2016 election: Trump aide John Mashburn had agreed to answer their questions.

But just minutes before he was slated to speak to lawmakers last week, the Democrat were told he had canceled — and wouldn't appear because Republican were not attending, according to three sources very well known the interview.

Democrats charged that Republican helped kill the interview after they learned Mashburn had agreed to attend, but Mashburn accused Democratic staffers in a statement to CNN of falsely claiming the interview would be bipartisan when they didn't tell Republicans about the session until an hour before it was scheduled to occur.