Not going to happen. You would need someone with the faux popularity of the ahoy polloi who could fund overnight. Not a general (wrong year), not a(n ex-)mayor, in fact not a political or business figure, because that's what you've already got. So unless you know for a fact Tom Hanks is running tomorrow on the America Party ticket and has ballot petitions going in all 50 states, your theory has no validity.
Well, I can’t believe the Dems just accept already that they lose this year. If they don’t try to split Trump’s vote, then Hillary bows out “for health reasons” and they run someone else...