Mr Bannon, who ran the hard-Right news outlet Breitbart, ended his White House role on Friday afternoon. He confirmed his departure in a message to the ABC news network.
He said he resigned. Sources close to Mr Trump said he was fired.
The decision was reportedly made after pressure from John Kelly, Mr Trump’s new chief of staff, who was brought in to establish some sense of order in a chaotic, dysfunctional White House.
Mr Bannon, 63, has taken immense pride at his status at the head of the anti-establishment, flame-throwing wing of the White House. He was seen as connecting Mr Trump to his electoral base, and encouraged nationalist, “America First” policies.
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