Here is a sentence one does not often get the opportunity to write: Bill de Blasio is right.

The progressive mayor of New York City is running for the Democratic presidential nomination, and he says former Vice President Joe Biden, another contender, “is out of step with the values of the modern Democratic Party.”

That’s absolutely true — and it is one of the few good things you can say about Biden.

Biden has irritated progressive sensibilities by telling wealthy donors that “nothing will fundamentally change” for them under a Biden administration and by praising the comity of his early days in the Senate, when he worked hand-in-hand with segregationist Democrats. Biden hated their racial politics, he says, but “at least there was some civility. We got things done.”

Sen. Cory Booker demands an apology, because apologies under duress are an important part of the political ritual of 2019, and to be able to command an apology signals that a politician is a real player. But Booker isn’t, so Biden won’t.

Not that an apology would save him.

Biden is trying to sell 1990s-vintage New Democrat centrism to a party that is high on outrage, vengeance and socialism. It would be a hard sell for a more ruthless and less feeble man.

There is a yawning class divide in the Democratic Party, and Biden is not the man to span it.

The party’s leadership is elderly, white and rich, while a good portion of its base is relatively young, brown and poor.

The latter understandably are getting tired of being told what to do by the former. They have heard quite enough from crazy ol’ Joe.

The Democratic Party is dominated by elderly white liberal children of privilege such as Nancy Pelosi (daughter of a congressman and mayor) and Cecile Richards (daughter of a governor), and Democratic leaders are perfectly comfortable among the super-rich: Pelosi reports assets amounting to as much as $202 million, from high-end San Francisco real estate to a Napa Valley vineyard.

Biden, who risibly advertises himself as “Middle-Class Joe,” owns a multimillion-dollar vacation home. Bill Clinton sports a limited-edition platinum Lange & Söhne wristwatch (and a few dozen more from Cartier, Roger Dubuis, Panerai and others) and even Barack Obama started wearing a Rolex after he was safely retired.

These are class markers — and for the resurgent socialists of the Democratic Party, they mark the rich and rich-adjacent bosses of the Democratic Party as class enemies.

The Al Gores and John Kerrys of the world enjoy rubbing elbows with Bill Gates at the World Economic Forum. Alexandria Ocasio-Cortez couldn’t find Davos on a labeled map, doesn’t want to and doesn’t need to.

The hot tickets in Democratic circles are expropriation and redistribution, not “nothing will fundamentally change” for the rich.

Democrats may not be ready to comfort the afflicted, but they are eager to afflict the comfortable.

Elizabeth Warren is proposing a radical and almost certainly unconstitutional — not that the Democrats care about that! — “wealth tax” that would seize not the income but the assets of well-off Americans, a scheme that has been abandoned even in Sweden, which progressives take to be the ideal state. (Sweden doesn’t have an inheritance tax, either — somebody should tell Bernie Sanders.) Whether such a tax would do anything useful is beside the point: It need not be productive as long as it is punitive.

What drives Democrats in 2019 even more than utopian socialism or the desire to be rid of Donald Trump is the desire to punish.

They believe that the poor are poor because the rich are rich, and that the unhappy are unhappy because Mark Zuckerberg and Jeff Bezos can afford to buy small planets.

The class of people they blame is the class of people Joe Biden has joined, whose goodwill he desires and whose fears he is working to assuage.

That’s a losing gambit for “Middle-Class Joe.”