It's tempting to call Donald Trump a cornered, wounded animal. But that gives him too much credit, understating the extent to which he is simultaneously becoming more pathetic and more terrifying.

Wounded animals just lash out at whatever wounded them; maybe whatever is in their immediate vicinity. They don't respond to losing a fight by pulling out a match and trying to burn down the entire forest.

And that is where we are after the third and mercifully final debate of this presidential election: left wondering if metaphors to which no other candidate would reasonably be subjected are too mild.

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The news media that Mr. Trump maligns as part of the grand conspiracy against him have spent many months trying to treat him like something approaching a normal candidate, and the campaign that he has turned into an embarrassing, humiliating circus like something approaching a normal campaign. Reporters have dutifully tried to understand his strategy and tactics, give his opponent similar scrutiny, and in many cases bent over backward to present this as a race between two flawed candidates.

Mr. Trump had perhaps earned that, despite the many odious things he has said and done – despite his flaws being on a different scale from ones that would normally have given Hillary Clinton a tough path – because he won the nomination of one of the two major U.S. parties fair and square. He benefited, though he apparently does not believe it, from respect for American democracy.

But surely we're past that now. Because Mr. Trump has signalled, in just about the clearest possible terms, that he doesn't believe in American democracy – that the likelier his rejection by voters appears, the more he will try to destroy the entire system.

In the previous debate, when his electoral prospects still looked a little better than they do now, he committed under some duress to accept the result win or lose. On Wednesday, given the same opportunity, he pointedly refused to do so. On the contrary, he sought to pave the way for his supporters to reject it along with him, by arguing weeks before election day that the process is rigged against him, and that his opponent should not even have been allowed to run.

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His camp will try, again, to defend him with false equivalencies. You can hear it, already, in the ludicrous invocation of Al Gore – a candidate who lost a recount under highly contentious circumstances, could have chosen to further inflame his enraged supporters, and instead delivered a gracious concession.

But this isn't Mr. Trump surrounding himself with women who once accused his opponent's husband of sexual assault, as repulsive as that was, to defend himself against video evidence of he himself boasting about assaulting women. Or comparisons between lax ethical standards at the Clinton Foundation and a different scale of sleaze on his part. Or trying to deflect his overt racism by invoking African-American backlash against Bill Clinton's justice policies.

This isn't just a matter of scale or context or fairness. Mr. Trump has done something no other candidate has done, and broken the one shared bond of rival candidates in every other election – a faith in voters to choose between them.

There will be much analysis, in the days ahead, about whether Mr. Trump really believes the system is rigged, or is just saying that to avoid the stench of defeat; whether this is about protecting his psyche or his brand. But it really doesn't matter, at this point, when the claims are demonstrably bogus and the ways they affect others so much more consequential.

Even if he does eventually concede, the damage may already be done. Millions of supporters, susceptible for various reasons to conspiracy theories about their country keeping them down, have been hanging on his every word.

Even before Wednesday night, he was using unsubstantiated claims of voter fraud to effectively encourage those supporters to go to polling stations on election day and harass minority voters. Now, he has all but called upon them to take to the streets if he loses.

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You have to hope, at this point, that more of them see him for what he is, and recognize that he's just trying to take them – and everyone else – down with him.