Republican presidential nominee Donald Trump speaks during a town hall in Sandown, N.H., on Oct. 6. (Evan Vucci/Associated Press)

In revealing himself as a vulgarian boor, Donald Trump exposed his fellow Republicans as spineless. When he denigrated the heroism of Sen. John McCain, most of the GOP stuck with him. When he mocked a disabled reporter, the party’s leadership shrugged. When he insulted Mexicans, Muslims, Gold Star parents and insisted until he no longer could that Barack Obama was born in Timbuktu or somewhere, the Republican Party looked the other way. Now, when a tape surfaced in which Trump confessed a yen for a married woman and in general talked about women the way Buffalo Bill used to talk about bison, the party has erupted in shock and revulsion. What happened? Easy. For the past week, Trump has looked like a loser.

Republican after Republican, looking at the polls and their own races, have concluded that Trump would not make a fit president. This realization came over them in a fit of self-interest, it somehow never having occurred to them before. House Speaker Paul D. Ryan disinvited Trump to a Wisconsin event, having suddenly developed an allergy to a man he has known all along is a liar, a deadbeat, an ignoramus and might have graduated from high school but remains a perpetual sophomore. He’d bring towel snapping to the Oval Office.

The same holds for the others who now find Trump repugnant. Former Utah governor Jon Huntsman, once an asterisk candidate of the presidency himself, withdrew his endorsement of Trump. He even suggested that Trump drop out of the race, possibly leaving a distraught nation with Mike Pence, an evolutionary marvel who has gone through life without a backbone. Rep. Jason Chaffetz of Utah reached the same conclusion: Trump should go. Throughout the Republican Party, there is a dawning: Something is wrong with this guy Trump.

Of course, we have yet to hear from Rudy Giuliani, who this week took a leave from his law firm — and his senses — to work full time for the Trump campaign. The former mayor of New York, who discerned “genius” in the way Trump did not pay taxes, has yet to discover brilliance in Trump’s mastery of the sexual vernacular and the suave way he approached women, but he is sure to come up with something. So, too, Newt Gingrich, who would like to be secretary of anything in a Trump administration. Alas, the polls suggest Trump will not be the next president. His Mount Rushmore will be some clown museum.

Trump has been useful. Like a litmus test, he has shown us politicians who have little principle, who have put their loyalty to the Republican Party over the good of the nation, who were willing to entrust the presidency to a man who, without any doubt, was as ill-suited for the presidency as Caligula’s horse was to be a consul of Rome. It has been a sordid show, both frightening and funny, and we can only hope it is over.