I think that's almost a more interesting question, who would be Trump's running mate? Who would Trump want and who would accept? Edit: The obvious choice would be an establishment republican, but who would do it? Trumps supporters are old, uneducated white men and women. How would he get the young, educated people? That's right, a Trump Sanders ticket :)
According to the news of the past couple days, Vladimir Putin. Me? I'd hold out for someone truly awesome, like Herman Cain or Sarah Palin. But if I were trump, I'd find an establishment wingnut with an actual political history. Which means Palin, Santorum, Gingrich or Huckabee. All of which would be hilarious. Even better would be like Bobby Jindal 'cuz it'd only take a week for Trump to say something outrageous about immigrants.
The GOP does not depend on the young and educated. :( Or non-voters.