Mitt’s out. The Republican told donors this morning that he won’t try for a third go at the White House, leaving the race wide open for Jeb Bush, Chris Christie and the rest of the GOP field. The announcement came amid signs of waning support for Romney, including the defection of Iowa strategist David Kochel to Bush’s camp. With Romney’s exit, the former Florida governor easily assumes GOP frontrunner status. Bush has already built a formidable apparatus that’s expected to post a massive fundraising figure for the first quarter. Run with it, Jeb.