Pretty sure Bush will win the nomination this time around, though it depends how the Ukraine develops.
If Ukraine reaches crisis point, meaning if the rebels are on the verge of taking all of Eastern Ukraine, then Hillary might well lose the election against someone like Bush.
That's going under the assumption of Hillary not convincing voters that she would stand up to Putin, or could handle a more aggressive Russia and China.
Do ou think there's an American who would say, "Hey, let's respond to a war we don't care about by putting another one of the crazy warmongers in office?"
Americans are basically selfish bastards. If we aren't being attacked, we don't care.