Given even the lowest expectations, Donald Trump still has the capacity to surprise.

In recent days, Trump has sneered at the looks of a woman who accuses him of sexual assault, denigrated the appearance of Hillary Clinton, proposed to drug test his opponent, used his campaign to promote what appears to be a Russian covert operation, asserted that Clinton has held secret meetings with international bankers “to plot the destruction of U.S. sovereignty,” attacked “Saturday Night Live,” promised to jail his opponent and contended that “the whole election is being rigged.”

Which means that Trump is sickeningly cruel, boorish, bonkers, subversive, conspiratorial, obsessive, authoritarian and reckless with the reputation of American democracy.

This is quite a closing argument for a presidential candidate. I imagine it did not emerge from focus groups. So what does all of this mean?

1. It means that the Republican nominee for president is frighteningly unstable under pressure. He is easily baited, highly sensitive to slights, prone to using faulty information from off the internet, hyperbolic and vengeful. Now imagine those characteristics during a confrontation with China in the South China Sea.

2. It is an indication of the quality of his closest, non-family advisers. Stephen Bannon and Rudy Giuliani are not attempting to keep Trump in check. They are feeding his manias. Trump is completely unmoored from restraining influences, and would be as president.

3. Trump’s closing case is a version, not of movement conservatism or tea party conservatism, but of crackpot conservatism — an alt-right rage against a vast, scheming establishment that includes the liberal media, global financiers and a growing list of women making accusations of sexual assault. All this was previewed during Trump’s political rise, which included birtherism, vaccine denialism and insinuations of foul play in the death of Justice Antonin Scalia. GOP leaders can hardly pretend to be surprised by this bent given that Trump accused Clinton in May of possible complicity in the death of Vince Foster.

4. It is a further indication (as if we needed it) that Trump has no commitment to the American political system. He is perfectly willing to delegitimize democratic institutions as a campaign tactic, squandering a civic inheritance he does not value. Even before his current troubles, he said that an electoral loss would be prima facie evidence of fraud and encouraged supporters to monitor majority-black polling stations in Pennsylvania. Now he is entering uncharted territory. By pre-emptively questioning the legitimacy of his forthcoming shellacking, Trump is stepping outside the four corners of the constitutional order, on the model of autocratic strongmen he has publicly admired.

5. Trump’s descent into ideological psychosis is tainting the reputation of all who were foolish enough to associate with him. Consider vice presidential candidate Mike Pence. Interviewed recently on “Face the Nation,” he defended the Republican nominee’s verbal assault — Trump has called them “sick,” “horrible” and “phony” — on women who accuse Trump of sexual assault. This reaction is justified, Pence said, because of Clinton’s “deplorables” comment. Here is one of the chief promoters of Christian morality in politics employing the ethical reasoning of 9-year-olds in the schoolyard. Someday Pence (and others) will look back on their shattered standards and ask: For this cause? For this man?

6. Trump’s final appeal is also corrupting a portion of the public and crossing moral lines that won’t be easily uncrossed. There are certain qualities of heart and mind that allow for self-government — civility, tolerance and mutual respect. In his rage and ruthlessness, Trump is inviting Americans to drink from a poisoned well. One problem is the risk of physical violence — the possible influence of unhinged rhetoric on an unbalanced mind. The broader result is radical polarization in which citizens question the legitimacy of elections and view some fellow citizens as enemies.

7. Practically, Trump’s downward spiral means that House Speaker Paul Ryan, Senate Majority Leader Mitch McConnell and Republican National Committee Chairman Reince Priebus will need to repudiate the nominee before the end — after they have shed the last of their credibility. The political argument against repudiation is admittedly strong. It could ignite a self-destructive civil war within the GOP just before an election. But history generally does not remember good political arguments. It remembers acts of conscience in the face of them. It is time, and past time, for Republican leaders to do the right thing.

Trump’s crackup complicates American political life in a variety of ways but simplifies one point: This man is temperamentally, ideologically and morally unfit to be president of the United States.