Mick Mulvaney is reportedly telling associates Trump can't fire him because he 'knows too much.'
Mulvaney would've been running the Office of Management and Budget when it withheld security funds from Ukraine, allegedly over Trump's desire to have Ukraine probe his political rivals, and he's also been right by Trump's side as the whole impeachment inquiry goes down. As a result, Mulvaney is telling his associates "there is no easy way for Trump to fire him in the midst of the impeachment fight."