If Tuesday’s vote in Wisconsin goes according to the polls, Donald Trump’s remarkable ride to the Republican nomination will crash into a wall. And if he never recovers his momentum, the postmortems will say his front-runner status was an illusion befitting a modern P.T. Barnum.

The postmortems would be wrong. Trump might well be stopped, but not because his campaign is a fraud. It’s because he’s blowing it.

Trump’s self-destructive conduct has me wondering whether he has a Gary Hart problem. No, not a “Monkey Business” secret, but a similar penchant for snatching defeat from the jaws of victory. The men are alike in using a hostile media to commit political suicide.

Hart, a former Colorado senator and the Democratic front-runner early in the 1988 presidential campaign, ended his promising career by spending a night with an attractive young woman not his wife. He tempted fate even as “womanizing” rumors dogged his campaign, and fate won.

On the day the Miami Herald outed model Donna Rice as the other woman, another paper carried an interview in which Hart had challenged reporters to ­“follow me around.”

“Follow me around, I’m serious. If anybody wants to put a tail on me, go ahead. They’d be very bored,” Hart had boasted.

It turns out the Herald had done just that, staking out his house ­after getting a tip, and struck ­paydirt.

Coincidentally, a poll that same day showed Hart holding a huge lead in the Iowa caucus, with 65 percent of the vote, and the eventual winner, Massachusetts Gov. Michael Dukakis, at just 3 percent.

A week later, Hart was out of the race and the National Enquirer soon published the infamous picture of Rice sitting snugly on Hart’s lap. He was wearing a big smile and a T-shirt bearing the name of the yacht they were on: Monkey Business.

Trump’s suicide-by-media efforts are of a different sort. He foolishly agrees to long interviews with news organizations that have already declared him unfit to be president, and gives them what they want. In his hubris, he provides the rope to the lynch mobs.

The New York Times, the Washington Post and MSNBC are the heart of the liberal-media batting order, yet Trump seems convinced their antipathy toward him is a simple misunderstanding and he can win them over with the brilliance of his blarney. When they ask him difficult but fair questions on NATO, nuclear weapons and abortion, he doesn’t flunk the tests; he blows them up.

Throw in the overwrought drama about the charges that his campaign chief grabbed a reporter, and Trump’s many enemies smell blood. He’s on defense instead of setting the agenda and is at risk of being sunk by his lack of knowledge and preparation.

Of course, many previous predictions of Trump’s demise have been premature, but he now faces the biggest hurdle yet. With only three names on the Wisconsin ballot, deep-pocketed donors are running attack ads just as Trump needs to expand his vote beyond the 37 percent or so he usually gets.

Instead, he’s going backward. What was a narrow lead for him has become a yawning deficit, with two surveys showing him 10 points behind Sen. Ted Cruz. In the RealClearPolitics average of the last six Wisconsin polls, Trump is in second place, pulling only 32.7 percent.

That’s trouble because Trump often underperforms his polls. Now he must overperform to have a realistic chance of winning a majority of delegates before the convention.

He shouldn’t kid himself about his predicament: If he doesn’t win the nomination on the first ballot, he’s not likely to win it at all. Enemies are multiplying faster than friends and he is rated favorably by only about 25 percent of Republican women, while 47 percent say they would never vote for him.

Trump’s crash, if that’s what we are witnessing, wouldn’t be just his loss. The nearly 8 million people who voted for him did so out of conviction that he alone was speaking for them. They feel abandoned by both parties and many of his supporters who write to me say they are praying that he doesn’t let them down.

He won their hearts with a ­relentless focus on jobs, immigration and trade. Those are the right issues, but neither Cruz nor Ohio Gov. John Kasich has seized on them in equally convincing ways, so Trump’s supporters would be abandoned again if he fails.

Two weeks ago, I wrote that I was seriously considering a vote for Trump in November. Unless he quickly snaps out of his funk, I won’t need to make the decision.

Sick of lies, Hill? Us, too

Now she knows how most of America feels.

The video clip of Hillary Clinton going wiggy after an environmental activist demanded she stop taking donations from the oil and gas industry captures her brittle sense of entitlement. “I am so sick of the Sanders campaign lying about me. I’m sick of it,” an angry Clinton said as she jabbed a finger toward the woman’s face.

In fact, the woman was right, yet the Great Dissembler shut her down by accusing her opponents of lying. No wonder 62 percent of voters say she is not honest and trustworthy — she’s not.

NY’s new bosses, same as the old

Once again, Albany proved itself impervious to embarrassment and reform. With two of the three previous men in a room headed for prison, their replacements comfortably took their seats with Gov. Andrew Cuomo and divvied up the $150 billion budget and imposed a new minimum wage and paid family leave on businesses.

When they emerged from their hidey-hole, the “leaders” showered themselves with praise and rounded up the votes to pass the package before most legislators could read what they were voting on.

Is this really the best New York can do?

Common sense is in detention

Don’t look now, but City Hall is erasing key measures of merit in New York schools.

First, suspensions for unruly students and other misconduct fell by nearly 32 percent, including a drop of 81 percent for insubordination. Advocates, including the New York Civil Liberties Union, cheered the decline, saying that too many of those who were being punished were nonwhite.

Now hardly anybody gets punished, which punishes all kids who come to school to learn. But who cares about them?

Second, parents and others who want to end standardized testing won a sit-down with Mayor Putz, which can only fuel their misguided campaign. Again, the issue is race, with one of the attendees, a Brooklyn principal, arguing that the tests somehow hurt black and Latino children and that parents should exercise their right to opt out.

Actually, what really hurts kids are adults who lack faith in the value of discipline and standards. Kids who grow up without either are doomed to a life of failure.