The Democrats’ white knight, Michael Bloomberg, might be a good businessman, but he has exposed fatal political weakness even before his presidential campaign is off the ground.

At the first whiff of criticism, he folded, apologized and repudiated the law-and-order policies that were his greatest legacy as mayor.

No wonder President Trump called him “a lightweight,” as Bloomberg squirmed to dodge the fallout from an old speech justifying the NYPD’s crime-fighting stop-and-frisk program.

“You’ve got to get the guns out of the hands of people … to stop [kids] from getting murdered,” Bloomberg says in leaked audio of a 2015 speech.

Ain’t that the truth.

Why apologize for policies that took guns off the streets and saved black lives?

Now, in the name of anti-racism, those policies have been dismantled and, presto, shootings are up 30 percent. Those who suffer most are in black neighborhoods, where an innocent child like 14-year-old Aamir Griffin was killed by a stray bullet last year while playing basketball in Jamaica, Queens.

Instead of cravenly disavowing his record, a Trumpian or Sandersian politician would turn the argument aggressively back on his critics.

He would declare that the real racism is to leave black children unprotected just so liberals can feel virtuous.

Instead, Bloomberg “apologized for everything he ever did, practically, and it’s pathetic,” said Trump, in a preview of what’s to come if the man he calls “mini-Mike” nabs the Democratic nomination.

Bloomberg, 77, also exposed a glass jaw after Trump teasingly said the 5-foot-8 ex-mayor needed a box to stand on for the next Democratic debate. Bloomberg’s indignant response was to call Trump a “pathological liar.”

It doesn’t say much for Democratic prospects that Bloomberg and his $2 billion war chest are ranking as high as third in national polls even before he officially joins the debate fray. Now that Joe Biden’s time on the Obama vapor trail is running out and socialist Bernie Sanders’ ascendancy is unchecked after a narrow, youth-fueled victory in New Hampshire, Bloomberg has become the hope of a party machine determined not to allow socialism on the ballot.

But of all Trump’s current rivals, it is Sanders, the president’s 78-year-old doppelganger on the populist left, who’s regarded as the strongest by some of the president’s closest advisers, including first son Don Jr.

North Carolina Congressman Mark Meadows is another Republican who says Sanders “is much more difficult to beat just because he’s able to run on an anti-establishment drain-the-swamp platform.”

“He’s a left-wing populist and when you’re giving away everything for free and not saying how you’re paying for it and the people who are getting the free things don’t care how you pay for it, it’s hard to compete with that.”

Biden’s collapse has left the Democratic establishment option split roughly between glib ex-South Bend, Ind., Mayor Pete Buttigieg, 38, and gritty Minnesota Sen. Amy Klobuchar, 59, neither of whom sets the world on fire. Then there’s Bloomberg or a wild card (Michelle Obama? Hillary Clinton?) to the rescue. Anyone but Sanders.

A random snapshot of the polling station at St. Anthony’s Catholic school in Manchester, NH, gives you an idea of the struggle ahead.

Of 4,400 eligible voters in Ward 7, where Democrats slightly outnumber Republicans and undecideds, Patty, 67, a retired payroll supervisor, switched from Biden to Klobuchar because “I didn’t think he could do it.”

Jim, 53, voted Biden because “I’m a union guy and he has the experience … even though he’s losing it,” he said, tapping his head.

I couldn’t find a Sanders voter who would talk. But Trump voters were not so shy.

“I’m a working man,” said Nate, 37. “Guess who I’m voting for?” A pipe fitter who commutes an hour to Boston, he said: “I work. I don’t want handouts. Trump has kept us in a job. He’s got a lot of things accomplished considering what the Democrats have been doing to him.”

Truck driver Jason, 48, from Lawrence, Mass., is voting for Trump because “he’s doing more for us than any of these clowns are going to do. Me and my friends are doing better than we were under Obama. I see it. Once he gets over all the crap they’ve pulled, it’ll be no holds barred.”

Michael Stimpson, 51, who manages a tool-and-equipment facility in Manchester, said “99 percent” of the 175 workers at his factory will vote for Trump in November, and New Hampshire will flip red because “things have never been better.

“Socialism looks good, until you have to live in it,” he said.

That’s the problem for Democrats: Trump voters are content with their economic lot and already have factored in the faults of the most investigated president in history.

The extent of the challenge is evident in the fact Democrats can’t decide which of two extremes to choose to combat Trump — a vacillating billionaire like Bloomberg or a rugged socialist like Sanders.

Even though we pretend politics is about policy, character and maybe money, the truth is that Sanders is the only other alpha male in presidential contention this year.

In the most primal sense, therefore, as dangerous as his ideology is, he’s the candidate with the best chance of surviving the looming cage fight against Trump.

Tom Steyer has spent $200M on his vanity

San Francisco billionaire hedge-funder Tom Steyer has spent almost $200 million on his vanity presidential campaign, for a grand total of about 13,000 votes in New Hampshire and Iowa combined. What a shameful waste of money. If he has a hole in his pocket, he should be helping the homeless and cleaning human feces off the sidewalks of his troubled hometown rather than lecturing the rest of us.

Stone-cold bias

It’s essential to avoid the mere appearance of bias in a politically charged case such as the prosecution of Roger Stone, the president’s friend. Yet the Mueller prosecutors’ seven- to nine-year sentence recommendation was manifestly excessive for a nonviolent crime, and their mass resignation looks like a political stunt.