Gretchen Whitmer, the Michigan governor seen as one of the Democrats’ best prospects to replace Joe Biden, has ruled out running, Politico reported Monday.But the swing state leader delivered a damning message to the campaign aide whom she called, the outlet’s Jonathan Martin reported, saying that the president’s debate performance will cost him Michigan.Whitmer called the campaign chair, Jen O’Malley Dillon Friday, after a day of frenzied speculation that she would be a frontrunner if Biden cou