Khizr Khan, whose son Humayun (L) was killed serving in the U.S. Army, speaks at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 28, 2016. REUTERS/Lucy Nicholson

Khizr and Ghazala Khan have forced Trump to confront a fact he cannot tolerate: his own insignificance. Relative to a soldier who died thwarting a suicide bomber, and to that soldier's grieving parents, Donald Trump is -- there's no polite way to put it -- nothing. The entire nation recognizes this, whether they admit it or not: the difference in stature between a carotene-hued reality toad and a Gold Star family.

Can we really say that a guy who has succeeded in becoming the presidential nominee of a powerful and once-venerable party is essentially a zero? We don't have to; Khizr Khan has said it for us. The nominee is "void" of "moral compass," "a person without a soul." And that statement rings true so loudly that Trump's closest allies have been forced into a sort of three-legged race: a doomed effort to outdo each other in expressions of heartfelt, meaningful hypocrisy.

House Speaker Paul Ryan in particular is bearing a special kind of misery, and is making a special kind of noise: the bleating we associate with a man who knows he has nothing credible to say. Ryan has become a walking liar paradox. How can he possibly address this situation in good faith? Whatever he states is made instantly hollow by what he is in the midst of doing to his career. Consider, for instance, the following virtue-drenched words:

"Many Muslim Americans have served valiantly in our military, and made the ultimate sacrifice. Captain Khan was one such brave example. His sacrifice -- and that of Khizr and Ghazala Khan -- should always be honored. Period." Sayeth Paul Ryan.

Unspoken is this: "I've decided to lend my reputation to a vainglorious putz who spits on this soldier's grieving parents."

Which is a bit of a problem. Period.

Khizr Khan puts this in stark terms: "There comes a time in the history of a nation where an ethical, moral stand has to be taken regardless of the political costs." Paul Ryan and Senate Majority Leader Mitch McConnell have a "moral, ethical obligation to not worry about the votes but repudiate him; withdraw the support."

The Donald likes to dismiss any critic as "a bad person," but even he recognizes that it's not wise -- for him, in particular -- to tar the Khans with that epithet. On the one hand, we have an aspiring tyrant who explicitly favors mass deportations and war crimes; on the other, a couple grieving for a son who gave his life for the principles that Trump hopes to unilaterally mangle.

The only way that Trump can survive this episode, I suspect, is if he apologizes to the Khans in a manner that is perceived as sincere. But that would mean backing down; it would mean admitting that he has committed a gruesome error. And he is constitutionally incapable of that. The Donald doesn't blink.

We may have reached a tipping point. By this I do not mean everyone's favorite cliché, but rather one of those warming rituals in which Lenin or Saddam's statue is tipped off its pedestal by citizens at last fed up with grotesque, swollen parodies of the human.

Justice rarely comes more poetic than this. Donald Trump may well be capsized by a couple who represent everything he fails to embody -- decency, patriotism, intellect -- and who happen to be members of a faith he wants to banish from the country.

Trump is being tilted from his huge gilded plinth by what has always made America great -- righteous immigrants -- when his own slogan, his very hat, strives to convince voters that he is uniquely that force: the greatness maker.

The Khans are members of a community that Trump has designated the country's most perilous enemy. And through the mere example of their humility and depth, Humayun Khan's parents have proven this libel to be no more than gaseous Freudian projection. You could hunt with dogs for the most clear and present threat to the republic, and those dogs (animals incapable of lying) would take you straight to Mar-a-Lago.

It likely doesn't matter to Trump all that much whether he is revealed as decent and patriotic, or loathsome and traitorous. Both make for epic ratings. What does matter, however, to a man who waxes apoplectic when journalists dare to point out that his hands are on the small side -- or when an artist suggests that his manhood may be more Seuss than Zeus -- is this revelation: that his whole being is stunted. That he is a little man. That he is no more capable of bestowing greatness upon a nation than he is of growing slender and elegant fingers, or apologizing to a grieving couple beside whose towering example he squats like the cheese-tinted mother of all garden gnomes.