Trump appointed Bannon his campaign's chief executive at the outset of the general election, and Bannon, along with now-White House counselor Kellyanne Conway, led the Trump campaign through Election Day.
The answer was a broad one.
A source familiar with the matter said Bannon was issued subpoena by House committee after refusing to disclose information from the time period of the transition and White House, as first reported by Fox News. President Donald Trump, provoking a subpoena from the panel's Republican chairman.
Collins was the first Republican member of Congress to endorse Trump in 2016. He was also slapped with a new subpoena on Tuesday from the committee itself, according to Rep. Mike Conaway, the Texas Republican leading the committee's Russian Federation probe, and committee chairman Rep. Devin Nunes, R-California, who still signs off on subpoenas. He has since had a major falling out with the White House. Following Sessions' testimony before the Senate Intelligence Committee, Democratic Sen.
"There were an very bad lot of questions we weren't able to answer based on this novel theory of executive privilege", he said.
"It's kind of a game of separation-of-powers chicken that's going on there", he said.
"The scope of this assertion of privilege, if that's what it is, is breathtaking".
Burck said in a statement that "executive privilege belongs to the President of the United States. If he's precluded from answering any questions during transition or administration and many questions even after he left the White House, obviously we're not able to do our job", Schiff said. Neither Bannon nor his lawyer immediately responded to a request for comment on Monday.
Bannon, 64, was a powerful figure in the Trump election campaign and the White House in the early months of Trump's presidency, pushing a hard-line nationalism aimed at shaking up USA domestic and foreign policy. That official spoke on condition of anonymity to discuss internal deliberations.
"Sometimes they actually have a White House attorney present in the room", she said. That person was not authorized to speak publicly about private conversations.
A spokesman for Mueller's office declined comment. "If the White House is permitted to maintain that kind of gag rule on a witness, no congressional investigation could ever be effective". And Wednesday, there were new signs other Trump associates would be less than totally forthcoming.
Bannon's remarks to Wolff are likely to be the focus of committee members. "It goes well beyond anything we have seen in this investigation", he added.