It was the most important intervention in modern political history. On the afternoon of Aug. 7, 1974, the two Republican congressional leaders and party patriarch Barry Goldwater met with Richard Nixon in the Oval Office to tell the beleaguered president that it was over.

When Nixon asked for a Senate head count against impeachment, Goldwater guessed that the president had no more than 18 loyalists left. Hugh Scott, the pipe-smoking Senate minority leader chimed in, “I’d say maybe 15. But it’s grim. And they’re not firm.”

The following day, Nixon — who always saw himself as the man in the arena battling until the end — announced his resignation.

There are Nixon veterans in the bunker with Donald Trump, notably disgraced former Fox News chief, Roger Ailes, and rightwing conspiracy monger, Roger Stone. They know the history of Watergate — and how lonely a political leader can be when his party abandons him.

After a day that should be remembered in GOP lore as Defection Saturday, the Republican presidential nominee could be down to a Nixonian remnant of maybe 15 shaky Senate supporters.

Early bailouts ranged from South Dakota’s John Thune, in charge of party messaging for the Senate leadership, to troubled New Hampshire incumbent Kelly Ayotte. In a feat of gymnastic dexterity, Ayotte has gone in a few days from hailing Trump as a role model in a re-election debate to claiming she misspoke to withdrawing her support.

Thune’s Saturday afternoon tweet advocated a wistful fantasy: “Donald Trump should withdraw and Mike Pence should be our nominee effective immediately.”

After impeachment, the Senate, of course, had the power to remove Nixon as president. The problem for alternate-reality Republicans, like Thune, is that only one man has the power to defrock the GOP nominee — Donald J. Trump.

To slightly simplify Republican rules: The verdict of the Cleveland convention is binding unless the nominee withdraws.

Imagine a delegation of Rudy Giuliani, Chris Christie and Jeff Sessions ascending to the gold-plated heights of Trump Tower to perform an intervention on the bilious billionaire.

What argument could they possibly make?

“Donald, for the sake of the party, we’re in an unsustainable situation. If you remain on the ticket, you will lose in a landslide to Hillary Clinton. Senators like Pat Toomey in Pennsylvania and Kelly Ayotte can’t survive the defection of women voters. Even the House might be in play.”

A normal politician might find that appeal sadly persuasive. But Trump would probably brag that his popularity is soaring based on six internet polls in which most of the voters were Russian bots. Moreover, he would likely snarl, “Why should I care about the losers on the Republican ticket? What have those traitors ever done for me?”

But the real stumbling block — and this would not be lost on Ivanka and the candidate’s sons — is the permanent damage that an October abdication would do to the Trump brand. Who would stay in a Trump hotel if the name were permanently associated with abusing women? Who would give Trump another TV show, unless it were soft-core porn? Women in Chinese factories might even balk at making Trump ties.

With post-election legal action against Trump University and probably the Trump Foundation on the docket, the GOP’s groper in chief has to place all his faith in another miraculous comeback from (moral) bankruptcy. Maybe a close finish — or an angry Election Day army of blue-collar men — would somehow save the Trump brand and the shaky fortune that depends on it.

Politically, Trump’s only hope is the long-shot theory that his supporters have already factored his vile personal behavior into their voting decisions. That somehow the shock and outrage triggered by the 2005 soap opera tape represents just the political and journalistic elites in both parties talking to themselves on television and Twitter.

Personally, I don’t believe that Trump will ever escape the stigma of his reprehensible boasts and behavior. But I can imagine Trump and his enablers convincing themselves that this too shall pass. Trump might even channel Richard Nixon, who said on a 1973 White House tape, “Despite all the polls and the rest, I think there’s still a hell of a lot of people out there, and from what I’ve seen … they want to believe. That’s the point, isn’t it?”

Sunday night’s debate could, in theory, give Trump a chance to write a new volume, “The Art of the Abject Apology.” But nothing about Trump‘s psyche suggests that he could emulate Nixon with his 1952 Checkers speech. Especially since Trump would probably demand that his cocker spaniel had to be a Ten.

Hillary Clinton — even if she is shrewd enough to avoid getting in the way of the Trumpian collapse — will have her own challenges on Sunday night. For the first time in months, she is poised for a sweeping victory on Election Day. This could be her moment to go beyond partisan talking points — and to reach out to the middle of the country in the hopes of creating a centrist governing majority.

There is something delicious about the detail that Trump’s downfall came as he headed for an appearance on “Days of Our Lives.” This has been the Weekend of Our Political Lives. And the Trump portion of the soap opera is slated to be canceled on Nov. 8.

Roll Call columnist Walter Shapiro is a veteran of Politics Daily, USA Today, Time, Newsweek and the Washington Post. His book on his con-man great-uncle was just published: “Hustling Hitler: The Jewish Vaudevillian Who Fooled the Fuhrer.” Follow him on Twitter @MrWalterShapiro.