You need to read the WaPo article on Trump's poll numbers. They arent a bubble like past flame out candidates more more like McCains or Romneys during their campaigns.
Yes, this is a real point and people aren't picking up on it for some reason. If you compare Bush/Carson (the leading GOP candidates) averages with 2012, they are hanging out with Dr. Ron Paul and Michelle Bachmann, not Romney. Romney's average almost never dipped below 20, and even when it did, only dipped as low as 18 for a few days. Bush's average is below 10.
The problem as I see it, is not that the Trump bubble isn't prone to burst, but that the Republicans don't have anyone competent to pick up the pieces when it does.