You'll see this situation is unprecedented, so history can provide no insight.
How EXACTLY is the 2016 "unprecedented"?
What is actually different in this election other than the fact that many who usually voting for the GOP are supporting a populist?
What issues are "unprecedented" in this election?
In EVERY presidential election candidates some niche to campaign on, Trump's happens to be immigration. The winner will typically NOT deliver on his promise (ask Obama why we're still fighting in the Middle East), but it doesn't matter because something else will come along and they will either do a good job with it or they won't.
Whether you support Trump or not, the fact remains that he won't be able to campaign on immigration and nothing else, people will lose interest.
Silver does make one good point, twelve years ago it looked like Howard Dean had it locked up on the eve of the Iowa Caucus and his campaigned collapsed almost overnight. The way the primaries are set up now, a candidate MUST win Iowa or New Hampshire to have a real shot and realistically they need to win both. One mistake in either of those states dooms a candidate.