As the Democratic presidential contest reaches the third state, what began as a coronation is now an exciting dead heat. Yet by one measure, Bernie Sanders is ­already a clear winner.

Regardless of whether the senator from Vermont captures the actual nomination, he has won the future of the Democratic Party.

Sanders is demolishing the last remnants of the old order, as represented by Hillary Clinton and her split-the-difference triangulation. It is Sanders, not she, who is the true heir of the radical politics of Barack Obama.

Calling a paradigm shift is like forecasting a recession — predict it often enough and you’ll eventually be right. Yet the developments unfolding before our eyes suggest the Democratic Party is undergoing a massive change. And a 74-year-old socialist is the architect.

A major piece of evidence is the enormous youth vote he attracts. In Iowa and New Hampshire, he beat Clinton by about 70 points — 84 percent to 15 percent — among voters under age 30. And despite the nasty demands by Madeleine Albright and Gloria Steinem that women must support Clinton, Sanders got 82 percent of the young female vote.

By contrast, Obama in the 2008 primaries typically beat Clinton among young people by about 20 points. With studies showing that most people stay in their first political party for many years, the young, ultra-liberal voters who turned out for Obama, and who are being joined by the Sanders wave, could dominate the party for a generation.

The implications are huge. Sanders’ call for a single-payer health-care system is a fantasy now, but it will outlive the campaign. His call for tuition-free public colleges won’t be forgotten, nor will his demands for enormous tax hikes on upper incomes. They’ll all be back as platform planks no matter what happens this year.

A second piece of evidence about Sanders’ impact is the way Clinton is jettisoning her incremental approach and embracing his anti-Wall Street, populist agenda. She’s calling herself a “progressive,” a word no one ever used to describe her, while also insisting that she is better able to get things done.

It would be an understatement to say the approach needs work. In New Hampshire, she urged voters to “bring both your heart and your head” on primary day — and promptly lost by 21 points.

There is, of course, an irrational dimension to the Sanders phenomenon. Obama is the most far-left president in memory, with his liberalism mixing higher taxes, an explosion of regulations and an expansion of social programs with a weak foreign policy.

The results everywhere are ­awful: The economy never fully recovered from the recession, and looks ready to slip back again. The world Obama tried to withdraw from is on fire, with talk of a global war growing louder.

America doesn’t need a double dose of the same bad medicine, but that is what young Democrats want. They believe Obama has been too moderate and see Clinton as even more old-school.

The party made this mistake before. After Lyndon Johnson ushered in the Great Society, a new generation furious about Vietnam pushed him aside for successors who were radicals at home and doves abroad.

Fortunately, most did not win the White House. Hubert Humphrey and George McGovern were rejected by voters, and Jimmy Carter probably would have been, too, were it not for the backlash over Watergate. After Carter’s disastrous term, the GOP won the next three thanks to Ronald Reagan’s pro-growth agenda and muscular foreign ­policy.

Dems won four of the last six elections, but Obama overplayed his hand. He scoffed at the center-left policies of Bill Clinton, and forfeited both houses of Congress. Now Sanders is going further by trashing the Clinton era in much the same way LBJ was trashed. He’s also daring to say Obama is not progressive enough.

Hillary is caught between Obama and Sanders, and, with the FBI probing her secret server and other issues, is under a cloud. ­Because of her trust deficit among voters, Sanders has more enthusiastic supporters.

Her message makeover is telling. Clinton initially hoped to build on her husband’s “third way” compromise between left and right, but no longer. Wall Street has gone from her piggy bank to her piñata.

Her husband, regarded affectionately by many African-Americans as the nation’s first black president, finds his welfare and criminal-justice record the target of angry young liberals. To save herself, Hillary last week discovered “systemic racism” in ­America.

Even if Sanders does not become president, the movement he unleashed is here to stay. So buckle up, America, the Dems are taking another hard left turn.

There’s a Rikers for a reason

City Council Speaker Melissa Mark-Viverito is on a mission to decriminalize many quality-of-life crimes, and hopes to close Rikers Island.

Her proposals are long on sympathy for people caught up in the criminal-justice system, but fall short on sympathy for the victims of the criminals she’s slobbering over. To her, only cops are bad.

Mark-Viverito, who engineered a raise for herself, from $137,192 to $164,500, is pushing legislation to wipe off the books 700,000 outstanding warrants for offenders who didn’t show up for court. They got initial summonses for urinating in public, breaking park rules, idling a vehicle, creating unreasonable noise or littering.

She called the move a continuing “quest for reform,” which might be true if the goal wasn’t a wholesale whitewashing of misdeeds.

Similarly, in her bid to close Rikers, she sounds as if the complex is another Abu Ghraib, the infamous Baghdad prison where American soldiers abused Iraqi detainees.

Top cop Bill Bratton negotiated with Mark-Viverito over her plans to stop many low-level arrests, and instead issue warnings. Bratton’s bottom line is that cops must retain the discretion to make arrests when they judge that appropriate.

In theory, that keeps a key policing tool intact. But cops already complain that City Hall undermines them, and the fear is that political pressure not to make arrests will lead the police to pull back on enforcement, as they have in other cities.

Gosh, ya think so?

Round up the usual denials. That was law enforcement’s first reaction when a Somali man named Mohamed Barry used a machete to slash four customers at an Israeli restaurant in Columbus, Ohio.

“There’s nothing to lead us to believe this is anything more than a random attack,” a police spokesman quickly told a local paper.

“Random.” That’s what Obama said about the slaughter of four Jews by a Muslim in a kosher market in Paris. “Random.”

Thankfully, the FBI soon took over the Ohio case and suggested terrorism was the motive. No kidding.

The one place they like Mike

Reader Ray Arroyo answers my challenge to identify a single state that Michael Bloomberg could win in a presidential bid. Referencing the former mayor’s campaigns against butter, salt and sugar, he writes:

“Bloomy wins the Nanny State…by a landslide!”