In the endless search for the magic key that Democrats can use to unlock the hearts of white people who vote Republican, the hot new candidate is “respect.” If only they cast off their snooty liberal elitism and show respect to people who voted for Donald Trump, Democrats can win them over and take back Congress and the White House.

The assumption is that if Democrats simply choose to deploy this powerful tool of respect, then minds will be changed and votes will follow. This belief, widespread though it may be, is stunningly naive. It ignores decades of history and everything about our current political environment. There’s almost nothing more foolish Democrats could do than follow that advice.

Before we proceed, let me be clear about what I’m not saying. I’m not saying that the desire for respect isn’t real. As a voter says in “The Great Revolt,” a new book by conservative journalist Salena Zito and Republican operative Brad Todd, “One of the things I really don’t get about the Democratic Party or the news media is the lack of respect they give to people who work hard all of their lives to get themselves out of the hole.”

Nor am I saying there aren’t some liberals who express elitist ideas, because there are.

But the mistake is to ignore where the belief in Democratic disrespect actually comes from and to assume that Democrats have it in their power to banish it.

It doesn’t come from the policies advocated by the Democratic Party, and it doesn’t come from the things Democratic politicians say. Where does it come from? An entire industry that’s devoted to convincing white people that liberal elitists look down on them.

It’s more than an industry, actually; it’s an industry, plus a political movement. The right has a gigantic media apparatus that is devoted to convincing people that liberals disrespect them, plus a political party whose leaders all understand that that idea is key to their political project and so join in the chorus at every opportunity.

If you doubt this, I’d encourage you to tune in to Fox News or listen to conservative talk radio for a week. When you do, you’ll find that again and again you’re told stories of some excess of campus political correctness, some obscure liberal professor who said something offensive, some liberal celebrity who said something crude about rednecks or some Democratic politician who displayed a lack of knowledge of a conservative cultural marker. The message is pounded home over and over: They hate you and everything you stand for.

This machine is extraordinarily powerful. It may not be able to guarantee Republican victory at the polls, but it absolutely can determine how conservatives — including those Trump voters — view what happens on a day-to-day basis in the political world, including efforts by Democrats to reach out to them.

Let’s take, for instance, Barack Obama. Can you think of another president who spent more time reaching out to the other side and showing respect for them? You might or might not like his policies, but nobody tried harder to be respectful than Obama. And Republican voters had eight years to watch him. Let’s take, as just one example, the speech he gave about race during the 2008 campaign. Here’s one small part:

“Most working- and middle-class white Americans don’t feel that they have been particularly privileged by their race. Their experience is the immigrant experience — as far as they’re concerned, no one’s handed them anything, they’ve built it from scratch. They’ve worked hard all their lives, many times only to see their jobs shipped overseas or their pension dumped after a lifetime of labor.”

That is extremely respectful. But it’s not what Republicans think of when they think of Obama. “I despise Barack Obama. I think primarily because I don’t think he thinks very much of people like me,” one Republican told The Post’s Dan Balz. “One of the places I would agree with the hard-core Trump people, they’re tired of being treated as the enemy by Barack Obama,” he went on. “His comment, the whole thing, it’s been worn out to death, that clinging to God and guns, God and guns and afraid of people who don’t look like them, blah, blah, blah. Just quit talking down to me.”

Ah yes, the “clinging to guns and religion” quote. One thing Obama said in 2008, taken out of context and repeated a million times until it was all any Republican voter needed to know about his entire presidency. But if you look at what Obama actually said, you’ll see that it’s different from the way it has been characterized. He was asked how Democrats could appeal to working-class whites in the Rust Belt, and he replied that people have watched their communities struggle for decades, through Republican and Democratic presidencies alike, so they wind up forming their political identities and channeling their frustrations through non-economic issues. Which few would actually dispute, but such controversies are rarely created out of what a Democratic politician actually said. They flow from whether it can be twisted around and repeated endlessly to make them look disrespectful.

The same is true of Hillary Clinton. At a town-hall meeting in March 2016, she was talking about how to revitalize communities that had been dependent on coal but had been devastated by a loss of jobs driven mostly by automation and the fracking boom that made natural gas cheaper than coal. Here’s what she said:

“And we’re going to make it clear that we don’t want to forget those people. Those people labored in those mines for generations, losing their health, often losing their lives to turn on our lights and power our factories. Now we’ve got to move away from coal and all the other fossil fuels, but I don’t want to move away from the people who did the best they could to produce energy that we relied on.”

Wow, that’s pretty respectful! It acknowledges the people’s hard work, their sacrifices, their contribution to the rest of the country. And yet because she also acknowledged that all those millions of coal jobs aren’t coming back, but said it in a way she would surely have liked to rephrase — “we’re going to put a lot of coal miners and coal companies out of business” — the only thing anyone remembers is that one half-sentence, which was immediately turned into “Hillary hates coal miners! She wants to destroy their lives!” All the respect-offering she tried to do was meaningless once it was chewed through the gears of the conservative outrage machine.

We see this again and again: Democrats bend over backward to show conservative white voters respect, only to see some remark taken out of context and their entire agenda characterized as stealing from hard-working white people to give undeserved benefits to shiftless minorities. And then pundits demand, “Why aren’t you showing those whites more respect?”

So when we say that, what exactly are we asking Democrats to do? It can only be one of two things. Either Democrats are supposed to abandon their values and change their policies, despite the fact that many of those policies provide enormous help to the very people who say Democrats look down on them, or they’re supposed to take symbolic steps to demonstrate their respect, which always fail anyway. How many times have we seen Democrats try to show respect by going to a NASCAR event or on a hunting trip, only to be mocked for their insincerity?

In the world Republicans have constructed, a Democrat who wants to give you health care and a higher wage is disrespectful, while a Republican who opposes those things but engages in a vigorous round of campaign race-baiting is respectful. The person who’s holding you back isn’t the politician who just voted to give a trillion-dollar tax break to the wealthy and corporations, it’s an East Coast college professor who said something condescending on Twitter.

So what are Democrats to do? The answer is simple: This is a game they cannot win, so they have to stop playing. Know at the outset that no matter what you say or do, Republicans will cry that you’re disrespecting good heartland voters. There is no bit of PR razzle-dazzle that will stop them. Remember that white Republicans are not going to vote for you anyway, and their votes are no more valuable or virtuous than the votes of any other American. Don’t try to come up with photo ops showing you genuflecting before the totems of the white working class, because that won’t work. Advocate for what you believe in, and explain why it actually helps people.

Finally — and this is critical — never stop telling voters how Republicans are screwing them over. The two successful Democratic presidents of recent years were both called liberal elitists, and they countered by relentlessly hammering the GOP over its advocacy for the wealthy. And it worked.

| Courtesy Spike Paul Waldman, op-ed mug.