Donald Trump. (Randall Hill/Reuters)

The Post's Dave Weigel sat in on a focus group of 29 Donald Trump supporters on Wednesday night in Virginia. It was run by Republican pollster — and focus group devotee — Frank Luntz. There's tons of fascinating stuff in Dave's writeup of the three-hour(!) session, but three sentences really stood out to me.

Over three hours in Alexandria, Luntz lobbed dozens of Trump-seeking missiles. All 29 in the group had voted for Mitt Romney in 2012. All either supported Trump, or had supported him earlier in the year. To Luntz’s amazement, hearing negative information about the candidate made the voters, only a few of whom gave their full names to the press, hug the candidate tighter.

So, yeah. That's absolutely remarkable, as Luntz told reporters afterward. “Normally, if I did this for a campaign, I’d have destroyed the candidate by this point," he said.

The broader conclusion to be drawn here — and the Luntz focus group reaffirms rather than reveals this reality — is that the people who are for Trump will almost certainly not be peeled off of him no matter what is thrown his way over the coming weeks and months. That's amazing.

I have started to think of Trump like C. Montgomery "Monty" Burns, the aging tycoon on "The Simpsons," in this regard. In one episode, Mr. Burns goes to the doctor for a checkup. He is told by the doctor that he has every disease known to man and "several diseases that have been you." But he's not sick because "all of [his] diseases are in perfect balance." They block one another from making him sick.

That's like Trump and his negatives. There are so many — including so many self-inflicted wounds — that they cause people who like him to simply say some version of "Oh, that's just Trump being Trump." If Mr. Burns is indestructible, then Trump is un-attackable. Everything bad is already out there about him. Oftentimes, he's said it about himself in some way, shape or form.

And it's not simply that normal political attacks against Trump don't work. As Luntz demonstrated in the focus group, those attacks actually make Trump stronger because they affirm for his supporters that he is different from all the politicians trying to bring him down.

For a candidate who was at 5 percent in polling, no big deal. For a candidate at 35 percent, according to the latest New York Times/CBS News poll, VERY big deal. Especially if that candidate is openly flirting with a third-party bid, and there's data out there that suggests he would bring 7 in 10 of his supporters with him if he abandoned the GOP.

At the moment, there is simply no scenario that I can conceive of in which Trump loses a large number of his supporters. Nothing he says. Nothing that is said about him. Nothing.

That means there is absolutely zero that establishment Republicans can do other than hope fervently that Trump's momentum slows or stops on its own or, somehow, he collapses under his own weight.

If you listen to the full Simpsons clip, the doctor tries to warn Mr. Burns that his health isn't perfect and that "even a slight breeze could...." Mr. Burns brushes past him, convinced he is indestructible. Remind you of anyone?