It won't be as simple as that. The republican party will be divided and full of in-fighting. Remember, we'll have to fight in senate elections too. If we can't produce a united front, we'll be seen as disorganized and without a message. If the democrats get a stong nominee who pulls the party together, we'll get slaughtered.
Rudy aside, I don't see any current candidate that will be able to "unite" us.
we are better off having fair primaries and debate, and all getting behind the winner, to stop Hillary.