The New York Times reports:
In selecting Mr. Priebus, the president-elect would passed over Stephen K. Bannon, the right-wing media mogul who oversaw his presidential campaign. If Mr. Trump had appointed Mr. Bannon, a fierce critic of the Republican establishment, it would have demonstrated a continued disdain for a party that Mr. Trump fought throughout his campaign.
Mr. Trump’s choice is certain to anger some of his most conservative supporters, many of whom expect him to battle the Washington establishment over issues like taxes, immigration, trade, health care and the environment. They view Mr. Priebus as a deal maker who will be too eager to push the new president toward compromise.In addition, Roger Stone says Priebus is Paul Ryan's boy:
-RWThe selection of @reince for COS in a @realDonaldTrump WH would cause a rebellion in Trump's base. #RyansBoy— Roger Stone (@RogerJStoneJr) November 12, 2016