Former U.S. Attorney William McSwain PHILADELPHIA - The top federal prosecutor in Philadelphia appointed by Donald Trump has written to the former president to seek his endorsement in a crowded Republican primary race to run for governor in next year's election.William McSwain's letter, dated Friday, was released Monday night by Trump even before McSwain has publicly declared his candidacy.McSwain has told Republicans in Pennsylvania that he is serious about running, and makes his intentions plain in the letter.