JACKSON, Mich. — Anita-Maria Quillen blended a strawberry-banana shake, tucked high heels into a Louis Vuitton bag and fired off last-minute requests at her little boys and their sitter.

She stepped out her door in flip-flops, where a waiting Chevy Tahoe would take her to a business fair near Detroit. The auto parts company Ms. Quillen has owned and run for six years, Diversified Engineering & Plastics, was profitable, but only because she had aggressively cut costs. She had whittled the payroll to 78 employees from 130. Now, the most important thing was to bring in new orders — what she called “working on the business, instead of in the business.”

Ms. Quillen, 35, belongs to a much-mythologized class in American life and politics: small-business owners. Politicians heap praise on them, campaigning in their factories and extolling their enterprises as engines of good jobs and good wages. President Trump’s election lifted their hopes for a resurgence.

But with the president’s economic agenda stalled in Congress, a more complicated reality was taking hold, especially in Ms. Quillen’s industry. After several door-busting years, auto sales had dropped every month in 2017. The slowdown had caught up to Ms. Quillen’s company, crimping her ability to contribute to the blue-collar revival that Michiganders had hoped for when they backed a Republican president for the first time in 28 years.

To own a small manufacturing business is to shoulder so many worries you hope your children find an easier career, and to realize how little the airy pronouncements of politicians describe your reality. Ms. Quillen, who voted for Mr. Trump, complies with the Affordable Care Act, but finds that employees who live paycheck to paycheck refuse to buy insurance at $150 a month. When her congressman visited D.E.P. and assumed government regulations must be a burden, she assured him, no, that wasn’t her problem.

What is a problem — what threatened her profitability and the nearly 80 paychecks she signs — was maintaining her niche in the auto industry, the backbone of Midwest manufacturing.

Carmakers are “constantly pushing costs down, costs down, costs down,” Ms. Quillen said from the passenger seat of the Tahoe, speeding east. “But meanwhile people want $15 an hour for minimum wage.”

Her 160,000-square-foot plant is filled with hulking machines that inject 500-degree molten plastic into steel molds. The resulting products — items like mirror brackets and window frames — go into Fords, Chevrolets and Harley-Davidson motorcycles.

But lately some of those machines have been idle. Her company had lost $3 million of work orders as of June this year. With unsold cars and trucks piling up on dealers’ lots, the big carmakers were getting ready to shut down their assembly lines for a few weeks over the summer. In a chain reaction, Ms. Quillen’s plant, too, scheduled a weeklong furlough in July.

The business fair she was attending, at a hotel in Dearborn, Mich., promised her the vital chance to meet buyers from Toyota and Fiat Chrysler, in the hopes of bringing new business in the door.

As a young female entrepreneur, Ms. Quillen prided herself on having the toughness to make a factory run efficiently. “I have a more challenging time with the more social aspect of things,” she acknowledged.

But she could not avoid putting herself out there forever. “I need to be out meeting people, establishing those relationships, getting those potential work opportunities in the door,” she said, as if giving herself a pep talk.

Turning to her administrative assistant, who was driving, she confided that a big D.E.P. customer seemed to be preparing to shift its injection molding work to China. “I’ve asked them point-blank, ‘Have you guys decided to source this somewhere else?’ ” Ms. Quillen said. “They told me no.”

She didn’t believe it. She had sources in the company. “If that’s their choice, I understand,” she said. “It’s a business decision. But don’t lie to my face. Man up. It’s not like I’m 12 and I told you I don’t want to be your girlfriend anymore.”

A Manufacturing History

The auto industry’s roots reach back more than a century in Jackson, a small industrial city ringed by farmland about 80 miles west of Detroit. A defunct Goodyear tire plant supported 1,500 workers in its heyday. Few factories in the area employ more than 300 now.

Jackson is typical of a certain kind of nonmetropolitan community: A generation ago, such rural and semirural places were responsible for 63 percent of the country’s new jobs, according to one recent study. Now, their share has dropped to just 35 percent.

The reasons include two familiar sources of social upheaval: the widening education gap between rural and urban residents, and a health crisis in rural areas gripped by opioid abuse.

Ms. Quillen, who employs 57 people on her factory floor, would like to create more jobs at higher pay in her hometown, where she went to high school and met her husband, Nick Quillen, a former teacher who now oversees the factory floor. (She bristles at suggestion of nepotism, though: “Do not ever refer to him as my husband,” she scolded an underling who made the mistake of doing so.)

But an opening for a machine operator, paying $9.50 to $11.50 an hour, can create a near crisis.

“Everyone jokes about millennials,” Ms. Quillen says, “but the generation younger than me, I’ve noticed their sense of responsibility to come to work is nonexistent.”

After two days of orientation, new hires are sent for a drug test. Sixty percent never show up.

The opioid epidemic has breached the factory’s walls anyway. Two D.E.P. workers were fired after overdosing in the past year, one in a company restroom.

‘We Take the Crumbs’

On a piece of plastic no bigger than a cigarette lighter rested great hopes.

It was a Friday in late spring, and Ms. Quillen was about to join a conference call with one of the world’s largest parts suppliers. In the automotive food chain, big suppliers like Delphi and Johnson Controls constitute Tier One. They sell directly to the carmakers. D.E.P., which primarily sells to other suppliers, is in Tier Two.

“Tier Ones are eating whole peanuts,” Ms. Quillen says mordantly. “We take the crumbs.”

D.E.P. was trying to take some control over its destiny.

Ms. Quillen was proposing to make a new part used in the transmission of General Motors vehicles. It had taken weeks to design and fabricate a prototype. Now, the little part sat on a conference table in the Tier One’s offices outside Detroit.

Ms. Quillen apologized for dialing in rather than attending the meeting. But it was also true that her own office was where she felt most confident, seated at a large L-shaped desk. On her windowsill were two copies of “Lean In” by Sheryl Sandberg of Facebook. She had been reading the new Ivanka Trump book, “Women Who Work,” which she praised for “good information, good suggestions.”

She sees herself as a driver of people, as a manager who places great demands on her workers and on herself. Others could find her intimidating. On one of her two Dell monitors was a sticky note to herself: “It’s About Feelings.”

“I built a wall around myself,’’ she had said earlier, describing how she rescued the company from years of unprofitability. “If I had allowed myself to be vulnerable, you get hurt, and if you get hurt you start to lose confidence in your ability.’’

“It’s sad, but I became immune to people,” she said.

On the call, the Tier One executive, a woman, expressed interest in the part D.E.P. had designed, but said it would seek competing bids from other injection-molding companies, of which there were many. “It’s our policy that we have to market-test the part,” the executive said. “You’d be competing against other suppliers that have the same capability.”

Ms. Quillen seethed. When the call ended, she turned to Zach Norkey, her sales manager, who had listened in beside her. “Did I not say this?” she said. “We did all this design work for them and they’re out quoting somebody else.”

She knew that D.E.P. would be outbid. Its own price, after all, factored in the design work the company’s engineers had performed.

Interactive Feature | Sign Up for the Race/Related Newsletter Join a deep and provocative exploration of race with a diverse group of New York Times journalists.

“We should almost walk away from this,” said Mr. Norkey, who had joined the company just four months earlier. “We’re going to end up giving them free consulting.”

“I’m getting used,” Ms. Quillen said.

The phone rang. It was D.E.P.’s manufacturer’s representatives — two freelance salesmen who work for several different companies. They had been at the Tier One’s offices during the call.

One of them proposed seeking a patent. Ms. Quillen said that would take years. The salesman said he had reminded the Tier One executive that D.E.P. was minority-owned. Ms. Quillen, whose mother is of Mexican descent, said she doubted that would count for anything.

“She doesn’t care what color my skin is,” Ms. Quillen said. “She just wants to only pay 5 cents.”

She worried that the Tier One would distribute the design specifications of D.E.P.’s prototype to other companies.

“The fact is, I want my part back,” she said, tapping her desk with a lipstick. “I want my information back.”

A Contrast with Her Father

Ms. Quillen has her father to thank for her place in life — and to blame.

Travis W. Pearse Jr. was a salesman: a manufacturer’s rep, like the men his daughter now employs. The son of a banker, he built relationships and won contracts over rounds of golf with buyers for the carmakers. He was so good at it that he was able to buy a controlling interest in D.E.P.’s predecessor company, Mid-American Products, in 2001.

Those were boom years. The company had 300 employees in three buildings on Wildwood Avenue, a commercial stretch between the airport and downtown Jackson. Employees referred to Building 3, where the executives worked, as “the country club.”

His daughter was at Michigan State, pursuing a childhood dream to become a doctor. One summer, she took a clerical job at the plant and fell in love with manufacturing.

It was controlled chaos, like on TV shows about hospitals, but with machines instead of patients. She left Michigan State and entered the business full time, first in personnel, then in purchasing.

Her father’s brand of relationship-driven deal-making was already on the decline when General Motors, Mid-American’s largest customer, sought bankruptcy protection in 2009 during the financial crisis. G.M. yanked away Mid-American’s largest line of business, a valve lifter guide, a part used deep inside an engine block, that provided 80 percent of its revenues.

Mid-American was soon forced into bankruptcy.

Ms. Quillen was 28. Her mother, Armida Flores, a retired high-school Spanish teacher, had joined Mr. Pearse in the business. Ms. Quillen watched as her parents, who had personally guaranteed company loans, nearly crumbled under the pressure.

Their daughter came to the rescue. Cashing in her 401(k) and mortgaging her home, Ms. Quillen and three partners bought Mid-American’s injection-molding machines and other assets, and reopened as D.E.P.

In hindsight, she blames her father’s people-pleasing ways, in part, for the bankruptcy. He was too trusting of his executives, too trusting of the automakers. “There is a huge difference between a salesman and a C.E.O.,” she tells him now.

Ms. Quillen calls her father forgiving, a warmhearted person, someone who can make anyone feel good. By contrast, she says, “I’m the tin man, seeking a heart.”

“What a joke,” someone wrote. “Time for miss prissy to get a real job instead of mommy and daddy taking care of her. Good luck in the real world Anita.”

She hid out in a restroom so no one would see her tears. “If your skin is not very thick, and you’re not a driven and dominant personality, an environment like this will just eat you up,” she says.

Taking over the business was not easy at all.

Her partners did not trust her to manage it, so they hired a president from the outside. Eyeing independence, Ms. Quillen earned an M.B.A. at night while continuing to work full time.

In 2013, she bought out two of her partners, eased out the president and began a scorched-earth campaign to reduce costs.

But her strict focus on the bottom line has put her at odds with advisers like an informal consultant, Milton H. Roye, Jr., a former G.M. executive, who visited D.E.P. in May. She admitted she had lost potential orders because the company was not growing fast enough.

“People always look at the top number, and I always look at the bottom number,” she told Mr. Roye in her office, at a table with a sculpture of the word “dream” between them. “I’m glad you make $15 million in sales revenue, but how much money did you make at the end of the year?”

Her banker, she said, loves her focus on the bottom line.

Mr. Roye steered the conversation to what he saw as a vulnerability: Ms. Quillen’s lack of personal effort building relationships in the industry. “I would embrace this weird thought Milton has that I, Anita, need to get involved,’’ he said. “Find out who some of the key people are to meet. Don’t send your V.P. of XYZ.”

Whiskey Shots to Celebrate

Weeks later, at the hotel in Dearborn, a poster on a gold tripod welcomed Ms. Quillen to the Michigan Hispanic Chamber of Commerce’s “Seventh Annual Diversity Matchmaker.” Toyota and Fiat Chrysler were “marquee sponsors.”

She circled the ballroom, her long hair tucked up in a conservative bun.

In every direction were steel bushings, aluminum engine components and all manner of plastic widgets. But after looking around, Ms. Quillen came to the conclusion that the big companies sponsoring the event had not actually sent representatives to do any business. Her 80-mile trip had been a waste.

On the last morning in June, a Friday, there was good news: The company controller reported that D.E.P. had had its most profitable month in years.

Ms. Quillen invited her executives to a toast at the end of the day, which was also the last day before the one-week shutdown.

“Just a brief story,” Ms. Quillen told executives as she uncorked a bottle of Jack Daniel’s Tennessee Honey. “I made a commitment that if we hit a certain monthly profit I would do whiskey shots. And we’re celebrating for this June that ended today, which is the best we’ve had in years.’’

Ms. Quillen walked the factory floor, hushed after the presses had been shut down and the shift workers had clocked out. Light from clerestory windows bounced off blue-painted walkways.

A message board on a wall silently cycled through announcements: the names of workers with perfect attendance in June; employee of the month.

She reached up for the power switch. She fumbled for it, searching the sides and the back of the monitor. Then she found it, and the screen went dark.