This piece will run in newspapers in my conservative congressional District in Virginia.

In terms of the law, and our Constitution's First Amendment rights, a presidential candidate is permitted to say pretty much anything short of a direct incitement to violence. But some statements are such transgressions against the constitutional order that they call out for special condemnation.

Donald Trump has said a great many things that have been not only offensive, but also damaging to the nation. Dividing groups against each other, for example - whether on the basis of race, religion, or ethnic background - clearly has a corrosive impact on a society.

But groups often have conflicting interest, and politics provides the arena where those groups can contend - peacefully - for power. And so, while racism and other forms of bigotry deserve criticism, the political conflict among groups is an intrinsic dimension of the democratic process. And thus expressing and addressing these conflicts has a degree of legitimacy.

But lately, Trump has committed a political offense that strikes at the heart of the political order.

It is hard to think of anything more fundamental to a constitutional order than its providing a nation the means to transfer power by peaceful means.

For millennia, frequently those at the top came to their power wading through the blood of their rivals. A major achievement in the history of civilization has been the replacement of violence by constitutionally-structured elections. By a solemn social contract, all agree to abide by the results of that constitutionally structured system by which the people make their choice.

Trump has struck a blow against this most fundamental foundation for domestic peace with his recent remarks like, "The only way we can lose, in my opinion, I really mean this, Pennsylvania, is if cheating goes on." He is saying there, in effect, "If I lose, don't accept the results." As Richard Cohen writes about this in his column in the Washington Post) : "It is serious business to question the legitimacy of elections... Trump, like a kid playing with matches, can start a conflagration."

When a presidential candidate makes such claims about "cheating" or a "rigged" election as we've heard from Trump, there are two possibilities.

1) If indeed those claims are based on clear evidence of a threat to the integrity of the election process, such accusations can be regarded as helping to safeguard the American political order. But

2) If such evidence is lacking, such accusations are an unforgivable assault on that order. They constitute a political crime, and such a dangerous assault should by itself be enough proof that this candidate is the wrong person for the job of being the nation's chief executive. How could a person who would so carelessly strike at the foundations of our constitutional order be chosen by the American people to be the person most responsible for protecting and defending the Constitution of the United States?

It really could not be clearer which of these two possibilities applies to Trump's ongoing effort to prepare his followers to reject the outcome of the election.

How can one possibly take seriously the claim that the only way he could lose Pennsylvania is if the other side cheats, when poll after poll - from a variety of reputable polling companies - show that he not only trails Hillary Clinton in that state, but trails her by a wide (possibly even double-digit) margin? And how can we take seriously a candidate warning about a "rigged" election when multiple professionally-conducted national polls likewise show him behind his opponent by more than we've seen in many election cycles?

Out of all the outrageous things Trump has been saying, this one in particular must be called out vigorously. No one can be allowed to sow the seeds of insurrection with impunity.

What's called for now is for the news media to confront Trump with a demand to "put up or shut up." They should demand either that Trump present the evidence to justify his claims that he can be defeated only by cheating, or that he publicly retract those claims. His followers - and indeed all the nation -- should hear from his own lips how unfounded and cynical his comments have been.

We've heard a lot of nonsense from this man over the past year. But this particular piece of nonsense is especially pernicious and dangerous and cannot be allowed to pass.

Andy Schmookler -- who was the Democratic nominee for Congress in Virginia's 6th District in 2012 -- is the author most recently of WHAT WE'RE UP AGAINST: The Destructive Force at Work in Our World-- and How We Can Defeat It.