Since writing last week that the moment of truth had arrived for Donald Trump, even I, and even at this late date, have been astounded at the frenzied amplification of the hysteria of his opponents within the Republican party and in the national press. Everyone seemed to detect that Wisconsin could be a turning point, and even very reasonable commentators such as Peggy Noonan and Kim Strassel in the Wall Street Journal wrote it up like generals giving battle in places advantageous to their enemies: Cornwallis at Yorktown, Napoleon at Leipzig, Hitler at Stalingrad and at Kursk.

Wisconsin was the state of the LaFollettes and the Progressive movement, and, despite the aberrant Joseph R. McCarthy, of Gaylord Nelson, founder of Earth Day, and of maverick Democrat William Proxmire. And the conservatives were authentic conservatives, such as the state’s able governor, Scott Walker, who has survived bruising battles with Democratic thuggery from the public-sector unions and from the shamefully politicized Democratic district attorney.

Another very respected Wisconsin political conservative is the speaker of the House of Representatives, Paul Ryan, who was drafted as vice president in the bumbling Romney campaign of four years ago, and was drafted again to the speaker’s chair after the sudden departure of John Boehner last year. Governor Walker has endorsed Ted Cruz, and Messrs. Trump and Ryan are far from soul-mates.

It was taken for granted by practically all observers that Mr. Trump would lose Wisconsin, though there was a wide variance of predictions of how badly he would lose. But implicit in many of the predictions was that any loss by Mr. Trump would be almost the end of his chances. It was deemed to be too late for a front-runner to lose and remain the front-runner, and there were comparisons with the almost Wizard of Oz campaign of Romney, in which he was momentarily rivaled or even surpassed in the polls after each debate – by Rick Perry, Michele Bachmann, Herman Cain, Newt Gingrich, and Rick Santorum.

But by this point in 2012, Mr. Romney was farther ahead than Mr. Trump. Of course, the comparison is nonsense, as Mr. Romney had been running for five years, having come second to John McCain in 2008, and was supported by almost everyone among the party regulars, including every living, dead, or anticipated member of the Bush family.

It was widely assumed that Mr. Trump’s gift for affronting conventional political opinion would finally swamp his candidacy after he allowed Chris Matthews to hound him into a mousetrap about abortion, and a few other indecorous reflections. These gaffes have poured out of this candidate in a syntactically challenged torrent since he was first dismissed as merely mounting a publicity stunt on the fringes of the stately procession to nomination of Messrs. Bush, Christie, or Rubio.

This has not been a campaign like the others and will not become one now. About 40% of this year’s Republican voters appear to be Trumpites more than Republicans and they don’t care about the offended sensibilities of the bearers of the conventional wisdom. Polls show Trump standing at close to 50% of Republican voters (i.e., registered Republicans and Republican-leaners) nationwide, which means that on top of the die-hards, some are attracted by his momentum or by the conventional judgment that he brings more to the (P)arty than John “Mr. Rogers” Kasich or Senator Cruz.

Mr. Kasich is a fine governor (Ohio) and congressional-committee chairman and could be a good president and very good vice president. Mr. Cruz has made a determined effort to carve out new ground to appease the survivors of the more conventional campaigns, clinging to their own wreckage, without alienating his natural constituency. Even Wisconsin Republicans are, in policy terms, much closer to Mr. Trump than to Mr. Cruz, but the electoral requirements are finally asserting themselves and Mr. Cruz is tacking to the center while Mr. Trump is becoming less shrill, but is not wrong in calling Mr. Cruz a Trojan Horse for the discredited party elders.

Conventional wisdom that burbled up from the celebrations anticipating the Wisconsin result, such as by Red Jahncke in The New York Sun on primary day, was that with a loss in Wisconsin, Mr. Trump would need 500 votes to get to the 1,237 needed for a majority at the convention, and that even though he seems likely to take everything in New York in two weeks, that will still leave him about 400 short with only about 600 more to be contested.

The widely held beliefs that the world is approximately round and that weighty objects generally fall downward are tepidly advanced speculation compared with the fervor with which the Trump-haters declare that if their anti-candidate falls one vote short at the convention in Cleveland in July, his vote melts like ice cream, he dies as a candidate, and he will have no influence on the outcome because all those who were hoodwinked into voting for him and serving as his delegates earlier will have recanted because his most vocal opponents have unmasked him as a charlatan and a menace to the planet.

There are some serious problems with this perspective. It emanates from sources that, whatever their earned stature and merit in other respects, have called it wrong at almost every stage of this campaign. That does not mean, of course, that they could not be right this time, but it should not be conceded on the basis of their previous eminence. One of the principal arguments that the Mr. Trump candidacy is fading is that he loses most of the polls in head-to-head match-ups with Hillary Clinton.

Mrs. Clinton should not be underestimated, but the same commentators who advanced this theory and savored a decisive Cruz win in Wisconsin did not much notice the ultimately unfeasible Bernie Sanders’s handsome defeat of Hillary Clinton there. Mr. Jahncke might want to contemplate the relevance of that, too, not only for what it could portend if the Clinton campaign started to slide more steeply, but also for what it means for the Republican nominee.

Whoever it might be could do terrible damage to a Clinton candidacy in a general election in which the Republicans will carpet-bomb the country with attack ads on every untruth and petty fiasco of Mrs. Clinton’s long and comparatively (to what happens in a presidential election) uncontested career. She won two elections in what was a large rotten borough in New York, having been the Wronged Lady of America, has little to boast about in her time as secretary of state, and has to suck and blow at the same time in invoking and distancing herself from Obama, all the while dodging the FBI on E-mailgate.

Wisconsin did not provide an adequate laboratory for testing what I called in this space several weeks ago the frontlash of those who resent the unprecedented smear campaign against Trump, its hyena tone and near uniformity in the media. I predicted, and still believe, that they will outnumber those who have joined and swollen that chorus. Only with trepidation do I cite myself, a foreigner, as representative of any echelon of American opinion, but it was gratifying to hear the incomparable Ann Coulter, who had been briefly bandied about by her most agitated critics as an apostate from the Trump campaign, hammer into pebbles the belligerent little bantam rooster of Wisconsin phone-in radio, Charlie Sykes.

Ms. Coulter told him, in her splendid Eleanor Roosevelt inflections, that she didn’t remember speaking to him, that no one would have heard of him outside the cow-milking counties of Wisconsin but for Donald Trump, and that he had completely misrepresented what she had said in a previous conversation. Yet Mr. Sykes arose, like a prairie apparition, and had his 15 minutes of national fame in Kim Strassel’s column.

There has been a great deal of mindless talk about an independent campaign. From the first days, Fox News was trying to impute to Mr. Trump the intention to run an independent campaign, which was nonsense. In the darkest days of the anti-Trumpers, there was talk of a spoiling campaign by the dismal likes of Rick Perry, enthusiastically floated by the chief Clinton house organ, the New York Times. In between were the castings of bread on the waters by Michael Bloomberg.

It was all nonsense. But what is not nonsense is the anger aroused by the disgraceful partisanship of the Republican National Committee in overtly fighting Trump — the leading candidate for leadership of the party for many months. If the Republican nominee, whoever that might be, wins fair and square, that person should defeat the Democrats, presumably Mrs. Clinton.

But if Donald Trump is sandbagged, there will not be the riots he offhandedly envisioned, nor will he waste a billion dollars putting Hillary in the White House; but the Republicans can kiss goodbye the millions of doubtful voters or outright habitual voting abstainers Donald Trump has brought to the Republican nominating process. There is plenty of room for reservations about Trump’s candidacy and his likely performance if he is elected, but cheating him of the nomination and discriminating against his supporters is Republican suicide. They will make the efforts of any such unfairly favored nominee so abject that even the hopeless flounderings of McCain and Romney will seem like cliff-hanging challenges for the great office.

Whatever may happen, Donald Trump has shattered political correctness and caused the 800-pound gorillas in the room to be identified: mass illegal immigration, unsuccessful trade agreements, and witless denial of the proportions of the threat of extreme Islam. If those who have followed him in this effort are treated like lepers by the forces of Republican continuity, especially if they hide behind the pantomime horse of Ted Cruz purporting to span from the radical centrists to the extreme right, the Republican party and the United States will be the losers. It must also be said that John Kasich’s poor showing in Wisconsin makes his continuation as a candidate very problematic, though he could reemerge quickly in a hung convention.

Given the convulsions he has already caused, Donald Trump, in one sense, cannot lose, but almost everyone else can. There is certainly a case to be made for a better candidate and a more desirable president, but only if that candidate emerges as a deus ex machina of instant and spontaneous solidarity, the traditional successful dark horse. (James K. Polk was practically the only one who went on to be a successful president, and that was in 1844 and in the other party, but theoretically it could happen again.)

Ted Cruz, who is very intelligent, could instantly reinvent a more conciliatory version of himself and be a unifying figure, but that is as difficult a concept as Donald Trump’s reemerging as a gracious and distinguished presidential candidate. Either or both could happen. But if Mr. Cruz ekes it out as the beneficiary of confected obloquy surpassing what was done to Goldwater (who would not have been a particularly good president), and rivaling what was inflicted on Nixon (a very successful president in his one full term), he will have an inauspicious launch. It remains, as the English say, all to play for.

Note: Last week, I inadvertently wrote that George H. W. Bush pulled out of the Pennsylvania primary in favor of Ronald Reagan in 1980. I should have written the Ohio primary, and apologize for my error.

— cbletters@gmail.com. From the National Review.