In 1993 Bill Clinton ask for the resignation of almost 100 assist. AG’s. and replaced them with his own choices.
I believe it is procedure for every appointed official to offer their resignation to an incoming President anyway.
In late 2006, the Bush Justice Department fired (or asked for the resignation of) eight U.S. attorneys all previously appointed by President George W. Bush. Earlier in 2006, a provision included in the reauthorization of the Patriot Act allowed these positions to be filled by the administration without U.S. Senate approval.
Remember the howls of protest from the left and media (but, I repeat myself) as these particular people had shown themselves to be partisan and Bush would not put up with it?