Imprisoned former Illinois Gov. Rod Blagojevich asked the U.S. Supreme Court on Tuesday to hear an appeal of his corruption convictions that included his attempt to sell an appointment to President Barack Obama’s old Senate seat.An 83-page filing making the request argues that the line between the legal and illegal trading of political favors has become hopelessly blurred, potentially exposing politicians everywhere to prosecution.“This case presents an ideal vehicle for providing the needed clarity,” it …