John Dean explains why Mueller's top aide could be the key to the whole hearing

On Tuesday, former Nixon White House Counsel John Dean explained to CNN's Erin Burnett why ex-special counsel Robert Mueller's decision to bring in his top aide, Aaron Zebley, could be highly consequential in his upcoming hearing with the House Intelligence and Judiciary Committees — and how House Democrats could take advantage of it to get more information on the Russia investigation.

"So, John ... you've got Aaron Zebley sitting next to Bob Mueller," said Burnett. "That was this last minute request, right? He was the deputy special counsel, he ran the day-to-day oversight of the Russia investigation. Now we understand that he won't be allowed to be sworn in by the Judiciary Committee, but the Intelligence Committee will allow him, according to Chairman Schiff, to answer technical questions. Why do you think Mueller wants him there? Is it to elaborate and give more information, or is it to sort of have a foil, a shield, from questions that he would prefer to not answer himself?"

"It's hard to speculate on precisely what he's got in mind," said Dean. "He may feel more comfortable with somebody who was much more granular in building the report than he was. He was sort of a big-picture guy and then probably made corrections. But he didn't work up the report in the same kind of detail that his chief aide did and can probably, you know, either whisper in his ear to refresh his recollection."

"And I think if the committee is shrewd, notwithstanding the fact he is not there as a witness, Democrats could certainly ask him a question," said Dean. "There is no rule that prohibits that. So we'll see how that plays out."

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