That's the magic Karl Rove question. The easiest way it could happen is if one of the professional lifer politicians decided to stop calling it "immigration reform" and admitted that it is an invasion of illegal aliens. If that had happened at any time in the last (10, 20?) years Donald Trump would not even be in the race.
Instead we have a spectacle of all the professionals standing around waiting for Trump to fail. Like watching a running back break away from all of the tacklers, and the defense waiting for the runner to trip and fall down.
We know that is not about to happen. Reality is not their strong suit nor is peeing in the rice bowls of their donors.
On the other hand, if tomorrow Trump called for a complete suspension of bringing any more Muslims into this country (while pointing out what they are doing now to Europe) and called for deporting most of the worthless hordes of Muslim parasites, assorted jihadists and non-assimilating Muslim cultist misfits Bush and 0bama both brought in to America since 2001 he could suspend his campaign right now, save the hassle, and simply show up for the Inauguration in January, 2017. He would be a lock and nobody could even touch him.