Last week’s debates removed any remaining doubt: The crazies rule the roost, with even the “moderate” Democrats pushing policies far to the left of President Barack Obama’s.

Some wailed about their competitors’ “unrealistic” visions and “fairy-tale economics” — even as their own ideas were straight out of the Brothers Grimm classics.

On health care, ex-Veep Joe Biden, supposedly one of the least extreme of the lot, says he wants to “build” on ObamaCare by adding a “public option” that (though Biden doesn’t say so) would inevitably replace ObamaCare.

The price tag: $750 billion — nearly the original estimated cost of ObamaCare itself. And Biden’s the moderate?

Sen. Kamala Harris complains that Biden’s plan wouldn’t cover all Americans. Hers would — by putting every American into government-paid health care within a fixed 10 years.

Sens. Bernie Sanders and Liz Warren, meanwhile, want to put the government in charge and end all private insurance — yesterday. Who cares if it costs $30 trillion-with-a-T over 10 years?

Rep. John Delaney pointed out one deadly flaw in all these plans, which would pay bills at Medicare’s rates, which don’t cover providers’ costs: “I’ve been going around rural America, and I ask rural hospital administrators one question: ‘If all your bills were paid at the Medicare rate last year, what would happen?’ And they all look at me and say, ‘We would close.’ ”

Delaney is one of the also-rans, with no chance of making the next debate. The same is true of Rep. Tim Ryan, who also offered occasional sanity.

They also fought over who’ll open the nation’s borders widest. Several, like Sen. Cory Booker and former Housing Secretary Julián Castro, promise to decriminalize illegal border crossings, making them merely civil violations — de facto open borders.

Warren backs that, too. But she also wants probes of how Customs and Border Protection and Immigration and Customs Enforcement agents have treated migrants. Show trials!

On climate change, Delaney slammed the Green New Deal — yet vowed to get to “net zero [carbon emissions] by 2050,” which is just impossible. Gov. Jay Inslee says, “We have to get off of fossil fuels in our electrical grid” in 15 years.

Andrew Yang almost comes off as the realist: We’re 10 years too late, he sighs. It’s time to “start moving our people to higher ground.”

On race, the extremism was less obvious, aside from the candidates pushing the fringe idea of taxpayer “reparations” to the descendants of slaves. When host Don Lemon basically asked the candidates to call President Trump a racist, they all jumped in — with Inslee even offering “white nationalist.”

Warren’s big applause line: “The president is advancing environmental racism, economic racism, criminal-justice racism, health-care racism,” leaving no slur behind. Thing is, Trump’s policies on all those fronts are utterly race-blind — Warren was simply forwarding the pernicious idea that any policy the left doesn’t like is racist.

Yet Sen. Kirsten Gillibrand likely won the “woke” sweepstakes with her offer to lecture white suburban women on “white privilege.” Never mind that the implication is that the vast majority of white Americans are racists, they just don’t know it.

Some of the hardest lefties, like Mayor de Blasio, will soon wash out along with the less-impractical candidates. But it seems certain that the survivors will all embrace what Delaney calls the “free everything and impossible promises” approach that will “get Trump re-elected.” Sad.