Jeb! is the most likely candidate. Republicans are not noted for being original thinkers, and when they try, they end up with PR nuisances like Agnew, Quayle and Palin.
The voters in the primaries will have much to say about who gets the nomination, but it probably will depend on who has the biggest pile of money, and that would be Jeb! who has forsaken his surname for the time being and added a ! to make him seem more exciting. And three letter names are easier to deal with that longer ones like Santorum, silly ones like Huckabee, and foreign-sounding ones like Fiorina, nee Sneed, Cruz, Rubio, or Jindal.
I see the Republican primaries as a great source of entertainment.
Keep in mind that I will have no input at all, I am only speculating based on observation of these creatures.