‘We’re voting with our middle finger,” a Trump supporter in South Carolina told a reporter last fall. No doubt.

Many a liberal observer saw the Trump vote as a rageful taunt aimed at racial and sexual minorities. But there is much more to Trump’s support than that, argues law professor Joan C. Williams in her new book “White Working Class: Overcoming Class Cluelessness in America.”

Making an admirable and research-driven effort to see things from the point of view of her subject, author Williams unpacks exactly how the white working class (WWC) viewed the election, and how their history-making choice made a lot of sense given their concerns.

The WWC is plagued by crisis within and without — household income in this group has been all but stagnant for 40 years. The mortality rate for whites 45 to 54 years old with no more than a high-school education has increased by 134 deaths per 100,000 people from 1999 to 2014. Opioids arrived and factories left. Democrats at best didn’t seem to notice; at worst they seemed to be causing misery by supporting NAFTA and mass immigration that drives down wages while imposing environmental policies meant to crush carbon-intensive industries. Then they mocked their victims as rednecks on the wrong side of history.

Williams isn’t interested in mocking her subjects. She is a liberal who is genuinely worried about the plight of the WWC. An admitted silver-spoon baby, she married someone she calls a “class migrant” — a guy from the working class (he’s an Italian-American from Bay Ridge, Brooklyn) who earned a spot at Harvard Law School, where the couple met. Right away, she was unable to hide her fascination with his people. At a family dinner, his father took a dislike to her because Williams seemed to be studying everyone like an anthropologist.

At a high school reunion, her husband returned home still using the habits he had picked up in the upper class, and it led to an uncomfortable moment. “What do you do?” he asked an old classmate. When you’re a lawyer or a financier, part of the global professional class, it’s a perfectly innocent question. Elites love to talk about their jobs, indeed define themselves by their professions. Not so the WWC. They see work devotion as an indicator of upper-class narcissism. They do the bulk of the boring, repetitive, unglamorous work, some of it physically demanding, and they don’t define themselves by their labors at all. That classmate of Williams’ husband replied spitefully, “I sell toilets.”

If your answer to the question “Who am I?” is “I’m a professor,” then your identity doesn’t change whether you’re in London, Miami or San Francisco. Elites have a tendency to leave home for college, then flit from one global capital to another. Not so the WWC, which Williams defines as white middle-class people (those in the $41,000 to $132,000 income range) who don’t have a college education. They’re strongly attached to their hometowns, to the people they feel comfortable with, to what they perceive to be the shared values of their communities.

Tradition and stability matter. “The dream is to live in your own class milieu, where you feel comfortable — just with more money,” Williams notes.

Donald Trump epitomizes this idea, having made his fortune “in garish casinos that sold a working-class brand of luxury.” Gold-covered everything is exactly how you’d decorate if you were from Appalachia and struck it rich with no intervening period of finishing school at Stanford or Yale.

To the rootless global elites, though, tradition is subordinated to transgression. What society considers edgy, elites deem worthy of their praise. It isn’t acceptable merely to accept gay life, for example — it must be celebrated. Recalling moving to San Francisco and observing a fully naked man walking down the street, Williams recalls feeling proud of herself for being tolerant of such norm-shattering. Among the elites, she says, “It’s a point of pride not to be one of those petty bourgeois who’s shocked by sexual transgression.”

This attitude not only stuns the WWC but strikes them as a kind of attack on everything they hold dear. To them, bicoastal urban America is a joke to which they don’t get the punchline. They feel excluded, marginalized, left out. Worse than any of this, they feel condescended to, and it infuriates them, Williams writes.

Hillary Clinton did a marvelous job of confirming their suspicions when she said — in New York City, at an LGBT event — that “You could put half of Trump’s supporters into what I call the basket of deplorables. Right? The racist, sexist, homophobic, xenophobic, Islamophobic — you name it. And unfortunately, there are people like that. And he has lifted them up.”

Being called names such as these is exactly what gets the white working class fired up. She might as well have told everyone from Pennsylvania to Wisconsin, “Don’t vote for me.” Outside of Chicagoland, they didn’t.

In one of Williams’ most compelling chapters, she explores how a strong connection to place helps explain why WWC don’t up stakes and move someplace where there might be better jobs. “I associate change with loss,” says one class migrant quoted by Williams, recalling that his father had repeatedly been evicted from apartments.

Instability is an insidious enemy from which the WWC feels a strong need to protect itself, having seen much suffering ensue from it, rather than the opportunity for exciting new adventures. Moreover, being rooted in a community has side benefits with real economic value that couldn’t easily be recovered after a move away from home.

She might as well have told everyone from Pennsylvania to Wisconsin, ‘Don’t vote for me.’ Outside of Chicagoland, they didn’t.

The WWC’s “lack of market power,” says Williams, “means that they rely on close networks of family and friends for many things more affluent folks purchase on the open market, from child and elder care to home improvement projects.” The additional expense of having to pay for child care previously arranged through social networks might nullify any economic gain from moving.

Trump’s base of support correlated strongly with areas where people don’t have college degrees. Why don’t these people just go to college? That isn’t a simple solution either. You might be condemned for trying to rise above your station.

“Getting a swelled head” is seen as an unpardonable sin, as J.D. Vance also discussed in his memoir “Hillbilly Elegy.” For the class as a whole, this is a self-defeating characteristic: How are people supposed to better themselves if their peers ostracize them when they even try? “I feel like I have changed sides in some very important game,” one class migrant says in the book.

Taking on a load of college debt is considerably riskier for a working-class family if you have limited resources. And the college environment is openly hostile to the WWC. “White trash” theme parties on campus highlight the last acceptable form of prejudice. Professors who would be horrified by a racist remark are perfectly at ease stereotyping, say, southerners as rednecks.

Even talking like a college person raises hackles among the WWC. The way managers and technocrats speak is seen as needlessly complex and phony; Trump’s vocabulary of one-and-two syllable words sounds refreshing to the WWC.

Direct, simple speech is seen as honest, and it’s important to maintain the same persona in every context. An auto mechanic quoted in the book says, “You know what I hate? Two-face. I can’t stand that. You’re a fake, you’re a fake. Why be a fake?” A Carnegie Mellon analysis of the final five presidential candidates remaining last spring found that Clinton was the one most likely to vary her vocabulary from speech to speech. Two-face.

That Trump declined to back down from his more colorful statements made him seem courageous and honest to the WWC, and they share his loathing for political incorrectness. The more he was attacked for being “offensive,” the more they were reminded of themselves.

Remarks that would end a career when overheard at a Georgetown cocktail party are utterly routine at the truck stop or on the shop floor, so every episode of pearl clutching at Trump’s rough talk felt like an attack on the way the WWC talks.

If even half of WWC women had voted for Clinton, today she’d be Madame President. But they voted for Trump by a margin of 28 points. That Clinton talked up being a woman didn’t appeal to them; the WWC doesn’t relate to talk of “glass ceilings.” Only elites worry about that.

WWC women want to spend less time at work, not more. They wish they had the option of being stay-at-home moms, and even if they were men they know they wouldn’t be in the running to be CEOs. A woman from Appalachia says in the book, “I’m voting to save my boyfriend’s job.”

Dismissing the WWC as racist doesn’t make a lot more sense than calling them misogynist, Williams argues, citing evidence that upper-class white people are simply better than the working class at camouflaging race-based judgments. You’ll rarely catch managerial types uttering racial slurs, but consider the “Greg/Jamal” study in which corporate recruiters were sent identical resumes, one from “Greg” and one from “Jamal.” The Jamals of the world proved to have a much more difficult time landing interviews.

As for why a $60,000 a year mechanic could feel affinity for a New York billionaire, it’s because WWC consider moguls to be fantasy figures. Trump represents something aspirational; they picture themselves in that boardroom firing people.

Managers, on the other hand, remind them of the bosses they resent. “Most working-class people have little contact with the truly rich outside of ‘The Apprentice’ or ‘Lifestyles of the Rich and Famous,’ ” Williams writes, “but they suffer class affronts from professionals every day: the doctor who unthinkingly patronizes the medical technician, the harried office worker who treats the security guard as invisible, the overbooked business traveler who snaps at the TSA agent.”

Hillary Clinton reminds them of the prissy know-it-alls who have been bossing them around their whole lives — she’s the lady who tells you there’s no eating in the library, as columnist Jonah Goldberg once put it. They don’t resent Trump, though: They imagine being him and firing her.

Clinton’s rhetoric about helping the poor also turned off the WWC: The have-a-littles disdain the have-nots. Working people in the middle are proud of their discipline and resent the spongers they perceive as being rewarded for having none. They don’t romanticize welfare recipients as being hapless victims of circumstance because they see them at the grocery store every week.

Even when they qualify for aid, they sometimes make a point of rejecting it: “I don’t want a government handout,” they say. “I can do this on my own.” Accepting welfare is seen as a character flaw and leads to a serious loss of social standing in the community, according to a study of rural voters in California. Without such standing, you don’t get considered when there’s a job opening.

Bill Clinton understood this kind of thinking, which is why he signed welfare reform in 1996, when he carried such states as West Virginia, Kentucky, Arkansas, Tennessee, Missouri and Louisiana. No Democratic presidential candidate since has won any of those states, and they’re no longer even trying.

Bill famously advised his wife’s campaign to do more to reach out to the WWC, but in what will surely be recalled as one of the defining moments of hubris on Team Hillary, campaign manager Robby Mook replied, “the data run counter to your anecdotes.”

It’s just too perfect that Clinton lost the election in part because she relied on a gay, 36-year-old Ivy League data nerd rather than a two-time winner of a presidential election to show her the path to the White House. If she wants to learn some anecdotes about how to repel people you’re supposed to be wooing, this book is an excellent place to start.

Kyle Smith is critic-at-large for National Review. Twitter: @rkylesmith