It’s been said that once a man makes bishop in the church or general in the army he never again eats a bad meal — nor will he ever be contradicted to his face.

This probably goes for billionaires, too — because if there was one crystal-clear takeaway from Wednesday’s debate, it’s that nobody’s been giving Mike Bloomberg any guff for a very long time.

He got a face-full in Vegas; he was startled by it, he was irritated by it, he didn’t handle it well — and now the questions are: Can he recover a credible debate form? Did he ever have one?

Either way, America is still likely to find out whether the Democratic Party is for sale — and perhaps the presidency, too.

For Mike Bloomberg is a stubborn old duck. He believes profoundly in Mike Bloomberg, and in the various missions he has assigned himself — if not entirely sincerely, then at least expensively.

Forbes says he’s worth $63 billion, up from $54 billion a year or so ago, and every uptick in the markets yields more grease for his political skids. (No wonder Bernie Sanders wants to crash Wall Street!)

And while the rest of America’s net surfers and TV viewers are coming to understand the breadth, depth and width of Bloombergian self-indulgence, New Yorkers have known all about it for some time now.

Bloomberg spent 12 years at the pinnacle of New York’s power pyramid. He got there — and stayed there — via one of the most audacious applications of checkbook-driven self-promotion in national political history.

The spending came in two streams — conventional and subterranean. That is, there was the obvious “I approve of this ad” sort, and then there was the much-more-subtle “Nice nonprofit you got there, buddy. Want some cash?”

No doubt the spending was all legal — though it was so massive it was hard to tell for sure, and nobody was paying attention anyway.

But just how massive? Bloomberg spent roughly 7 percent of his then-approximately $4.5 billion fortune — somewhat north of $315 million — up front and in the open.

How much went quietly to what are euphemistically known as “community influencers” these days is a mystery — but whatever the sum, it was effective. In a city infamous for policy intimidation by public demonstration, City Hall’s steps went mostly silent during his tenure.

Since leaving office at the end of 2013, he has expanded that sort of spending nationally — indeed, globally. He has been embracing causes and concerns that come with prefabricated, energized and hugely combative interest groups and organizations.

He lavishes cash on anti-gun activists; on climate-change warriors; on institutions with outsized roles in the national health-care debate; on local good-government wonks; on small-bore mayors everywhere and so on — creating along the way political force-multipliers owing debts callable at Bloomberg’s discretion.

His opponents will disregard this shadow army at their risk; none of its soldiers want Mike’s money to dry up.

Meanwhile, Bloomberg has never been bashful about spending big to influence — if not suborn — government policy to his advantage. Didn’t he get the New York City Council to lay aside Gotham’s two-term-in-office limit to allow a third for himself?

Now comes word that Private Citizen Mike is subsidizing state attorneys general for climate litigation — about as egregious a violation of the principle of democratic self-government as one can imagine.

And it’s certainly not unreasonable to view the $100 million he spent to elect Democrats to the House in 2018 as a down payment on a compliant Congress in 2021 — should it come to that.

Clearly he has been planning this run for a very long time, and while America has never lacked for unconventional rich guys seeking high office, sometimes they get elected.

Bloomberg, of course, is in a class by himself.

He says he’ll spend whatever it takes to get the job done — which would be $4.4 billion, applying the 2001 New York mayoral 7 percent-of-net-worth standard. And 10 percent — $6.3 billion — wouldn’t be out of the question, would it?

Whether the voters would choke on that is an open question (one hopes so), but this much is certain: Mike Bloomberg has the resources to shove Wednesday night’s dubious debate performance down the memory hole in short order.

Who’s to doubt that he’ll be around for a while longer?

Twitter: @rlmac2