Less than a month before the election, the Republican speaker of the House says he won’t defend or campaign with his party’s presidential nominee. The nominee has responded by slamming the speaker on Twitter, and his campaign manager is accusing some (unnamed) elected Republicans of sexual harassment against her.

The Donald Trump campaign and the Republican Party show every sign of entering into an ugly death spiral. The revelation of the Trump “Access Hollywood” tape last Friday occasioned a historic rupture, with elected Republicans around the country denouncing Trump and calling on him to step aside.

Any hope of Trump turning a corner with his relatively competent second debate was dashed when House Speaker Paul Ryan told his colleagues that he is concentrating on saving his House majority as a check on Hillary Clinton.

It is a fact that one out of two major-party presidential campaigns fail. Some fail badly. But the GOP may be about to experience an unprecedentedly wrenching debacle because its nominee is an ideological interloper with no impulse control or regard for political norms. No matter how bad or weird the campaign seems now, it could get worse and stranger still.

Bob Dole was a horrible presidential candidate and not a particularly conservative Republican. But he was an honorable man who had a loyalty to things bigger than himself, including his political party. When Republicans had to cut him loose in 1996 to try to save their congressional majorities, he was a good and loyal solider.

Does anyone expect that of Donald Trump? His investment in the party is nil, and he takes all slights personally, whether they are from Alicia Machado or the speaker of the House.

The “Access Hollywood” tape was a tipping point. In isolation, perhaps Republicans could have looked beyond it. But after so many controversies and interventions and alleged pivots, the dam finally broke.

Trump depended on brute force more than on persuasion or personal relationships to unite the party. Many Republicans were tentatively and insincerely aboard the Trump Train to begin with. They went through the motions in public, while conceding in private Trump’s failings and worrying about the consequences of his candidacy.

None of them will ever be up for Profile in Courage Awards. Not coincidentally, they broke with Trump as the polls began to slide the wrong way, with the latest NBC/Wall Street Journal poll showing him down by double digits. (Nothing pricks a politician’s conscience like bad poll numbers.)

The split over the past few days creates the predicate for a GOP internal war until November and beyond. It will pit swing-state Republicans and those who want to save them, like Paul Ryan, against Trump’s hard-core base and the balance of ordinary partisan Republicans who want the party to fight even harder for Trump. The disunity itself will be damaging and dispiriting.

There will be every incentive for Trump to exacerbate rather than try to smooth over, or at least look past, the divide. Hitting back at his party critics energizes his fans, and, if he is headed for a loss in November, it sets up a stabbed-in-the-back narrative after the election. So his party detractors are insiders, quislings and, to believe his campaign manager Kellyanne Conway, sexual harassers.

The period before the first presidential debate, when Trump pulled close to a tie with Hillary Clinton, feels like an eon ago. He had come back with a month of relative discipline beginning in mid-August that now looks like a parenthesis in an otherwise recklessly selfish campaign.

That Trump would become a poisonous wedge issue within the GOP was always a plausible worst-case scenario. Now, it is upon us. Trump supporters in the primaries wanted to “burn it down.” They may well be able to point to the wreckage of the post-November GOP as an indicator of their smashing success.

Rich Lowry can be reached via e-mail: comments.lowry@nationalreview.com.