Kyle Sampson, Gonzalez’s Chief-of-Staff explains in an e-mail to Harriet Miers. Rove attempted to say that the replacements were sort of like finally getting around to replacing holdovers. Not true.
The only case involving hold overs is the acting US Attorney in Guam in 2002. The acting US Attorney had been acting for 12 years–since the Bush I administration. Making someone permanent makes perfectly good sense in such a case, but it oddly came one week after the acting US Attorney for 12 years reported he was opening an investigation into Abramoff. Of the seven that are at the center of the controversy right now, all were Bush appointees.