Thanks to the recession, we all know about financial bubbles and the damage they cause. But are there such things as political bubbles? I say yes, and believe America is in the midst of one now.

The idea grows out of a book that dissects a financial bubble that popped nearly 300 years ago. In “The Great Mirror of Folly: Finance, Culture and the Crash of 1720,” three Yale professors recount how stocks in France, Britain and the Netherlands soared by 1,000 percent, then crashed.

The authors, according to a Wall Street Journal article, don’t accuse investors of being irrational. They included Isaac Newton and believed new corporate structures would protect them and that trade with the New World marked a global transformation.

In the long run, they were right. But caught up in market mania and blind faith in momentum, they dramatically overpaid for stocks.

That is common bubble behavior, but a similar mania can happen in political movements and turn them into bubbles, too.

For example, one of the book’s authors told the Journal that a clear sign of a market bubble is when investors discount all evidence that doesn’t fit their belief.

He called that a “hinge point” that leads investors to a “binary framework where anybody who disagrees with them is demonized.”

That perfectly describes the cult of Barack Obama and the bubble of liberalism he embodies.

They are built on blind faith in his personal exceptionalism, discount facts and are sustained by a demonization of doubters.

Indeed, Obama’s career is something of a faith-based movement.

Despite his lack of experience and record, he was elected on the promise that he could get government to do what it had never done before. He shaped and benefitted from a belief that this time was different, that the old rules didn’t apply.

“We are the ones we’ve been waiting for,” he said in promising a unique period in history. “We are the change that we seek.”

He persuaded enough people to buy his stock that, in hindsight, its momentum carried him beyond any reasonable explanation. That bubble is still expanding but only within the Democratic Party. Case in point is the election of far-left Mayor Bill de Blasio and Speaker Melissa Mark-Viverito in New York.

A recent Clarus survey on ideological trends finds that 43 percent of Democrats now self-identify as liberal, up from 29 percent in 2000. Meanwhile, Dems who call themselves moderate declined by 8 points, from 44 percent to 36.

Based on the failure of Obama’s key policies, that rapid shift to the left isn’t rational.

Slow economic growth, high underemployment, rising national debt, bitter polarization at home and spreading global disorder show that the faith in liberalism far exceeds its actual performance.

Fortunately, most Americans get that, as reflected in the rise and fall of Obama’s standing with all voters.

His approval ratings hit about 70 percent in his first year but stood at 38 percent at the end of his fifth year. Millions of Americans concluded he is not the president they believed they were buying. In effect, they realized they overpaid.

Now they are selling and his stock is tumbling. It is down by more than 40 percent as Hope & Change has given way to incompetence and ObamaCare.

Nearing their crash, financial and political bubbles share another feature. As the Yale authors put it, the “hinge point” reflects the irrational fury of investors who try to silence nonbelievers.

That moment is upon us with liberalism’s bubble.

Dare to doubt Obama and you are demonized by him and his followers.

A recent letter from one fits the formula. After I denounced Obama’s smears of Senate Dems who opposed him on the Iran deal, reader Tom Matyas said I belonged in North Korea or China, and added: “You are apparently among the morons who believe Obama set the IRS on the Tea Party even after it has been debunked by any rational analysis and that the financial stimulus was a waste when actually it was too small, like your intellect . . . Get a life, Bozo.”

Desperate “investors” like that mean the Obama bubble is ready to pop.

PS 106 is deplorable, and parents who allowed it to happen share blame

The articles by Susan Edelman and other Post reporters about the deplorable conditions in PS 106 are compelling. They feature a principal who is often absent, a lack of books and a bizarre ritual that turns a fifth-grade graduation into an expensive, prom-like event.

The “School of No” is in the Far Rockaway section of Queens, and it’s clear these outrages would never happen in most schools. Parents simply wouldn’t let the city get away with it.

That truth reflects the most important dividing line between haves and have-nots. It’s not poverty or race or geography.

It’s parents who are involved in their children’s lives. There is no superior substitute.

Gov. Cuomo must follow through on promise to lower taxes

Gov. Cuomo’s promise to deliver $2 billion in tax cuts was easy to say, but hard to do. So says the Citizens Budget Commission after examining the budget.

Cuomo will flesh out his plans Tuesday, but the watchdog CBC argues that he can keep his promise only by imposing serious restraint in nearly all agencies.

Analysts Elizabeth Lynam and Jamison Dague say Cuomo must limit the overall spending increase to 2 percent to produce a surplus for tax cuts, because Medicaid and education are both growing at 4 percent. They spend 40 percent of the $94 billion budget, meaning smaller growth or cuts must come elsewhere.

Here’s hoping Cuomo doesn’t go wobbly.

Robert Gates humorously reflects on days in the CIA

Former Defense Secretary Robert Gates is taking an unfair beating over his book, “Duty,” but hasn’t lost his sense of humor. When TV interviewer Charlie Rose said his career in the CIA probably made him “suspicious” of Iran, Gates smiled and said:

“There’s an old line about intelligence officers that when they smell flowers, they look around for the coffin.”

As they laughed, Gates added, “So, yes, I’m suspicious.”

Poll debunks de Blasio notion that Bloomberg was bad for NYC

A new poll ought to give Mayor de Blasio pause about his mandate. By a lopsided 64-24 percent, New Yorkers call Mayor Bloomberg’s 12 years “mainly a success,” a finding that undercuts de Blasio’s resolve to turn the page on the Bloomberg years.

Voters also tell Quinnipiac University by a margin of 61 to 18 percent that they didn’t like the criticism of Bloomberg at de Blasio’s inauguration. Respondents from every group agree by at least 2 to 1 that the attacks were inappropriate.

Each poll is just a snapshot, but this one is consistent with others showing that most New Yorkers don’t want Gotham to be radically transformed. While there is support for de Blasio’s planned tax hike on the wealthy, voters don’t agree with him that income inequality is Public Enemy No. 1. Sensibly, they are most concerned with schools and jobs.

Those are the areas where de Blasio should put his energy. If he doesn’t, he could find himself an unpopular mayor in an unhappy city.