NEENAH, Wis. — In Winnebago County, they’ve seen the paper mills close, one by one.

While Kimberly-Clark, founded here in 1872, still employs several thousand people locally, abandoned mills dot smaller towns in the region. Paper production has moved to cheaper locales overseas with less stringent pollution rules. That has left a pall — and a sense of fear and insecurity — hanging over places like Neenah, even as factories in other industries are still humming.

For many, the villain is trade.

Take Neenah Foundry, a 145-year-old operation that employs nearly 1,000 workers here. Its employees have watched in frustration as cheap manhole covers and sewer grates flood into the country from India and elsewhere, where competitors are eligible for government subsidies and face fewer environmental regulations.

“For a long time, trade hasn’t been fair,” said Jeff Lamia, who started work at the foundry earning $5.35 an hour, fresh out of high school nearly 40 years ago, and now makes $27 an hour.

“They can build stuff for pennies in China with no environmental rules,” he added. “Our foundry has an ungodly amount of emissions controls and that costs big money. Overseas, they throw it out into the air and we have to compete. That’s not a level playing field.”

More than a year after Donald J. Trump’s victory, it’s easy to forget that the seemingly tectonic electoral shift came largely from 80,000 voters in Wisconsin, Michigan and Pennsylvania who moved those reliably Democratic industrial states into the Republican column.

Few places embody the underlying economic and political dynamics of that switch more than Winnebago County. Almost a third of Wisconsin’s 72 counties flipped from blue to red, and like most of them, Winnebago is heavily dependent on manufacturing, whether in gritty blue-collar towns like Oshkosh and Menasha or in Neenah, which is home to both factories and corporate offices downtown.

Indeed, with one-fifth of its jobs in the factory sector, Winnebago is more dependent on manufacturing than over 90 percent of the nation’s counties. As a result, residents worry about foreign competition for locally made products like Oshkosh trucks or the fire engines built by Pierce in Appleton and exported around the world.

And with the North American Free Trade Agreement hanging in the balance, and the possibility of a trade war rising, White House decisions on trade in the months ahead will reverberate here and in other Midwestern states — and may determine whether last year’s political shift becomes more enduring.

Mr. Trump’s attacks on free trade and promises to bring back good-paying jobs from overseas resonated deeply here — even with lifelong Democrats like Mr. Lamia. Those issues, along with a growing disdain for politicians in general and Hillary Clinton in particular, prompted Mr. Lamia to choose Mr. Trump after voting for Barack Obama in 2008 and 2012.

Other foundry workers like Jeff Olejnik, a Democrat who couldn’t bring himself to vote for Mr. Trump in November and reluctantly supported Mrs. Clinton, admits that his message on trade was compelling.

Winnebago County, Wis. Winnebago County, Wis. WINNEBAGO U.S. Population 169,900 323 mil. Percentage white 89% 61% Median household income in 2015 $52,000 $52,900 2.8% 4.1% Unemployment rate Manufacturing share of employment 20% 7% ELECTION RESULTS 2012 2016 47% Romney Trump 50% Obama 51% Clinton 43% By The New York Times | Sources: Bureau of Labor Statistics; Bureau of Economic Analysis

“We need to take care of our people here,” he said. “There are at least a dozen paper mills in this area that have closed. You are losing good-paying jobs.”

“People in the Midwest don’t ask for much,” he added. “They want to take a vacation once a year, have decent health care and enough money to pay their bills and save for retirement. That’s our life, but pretty soon there won’t be no middle class.”

For many who have made a life in Neenah, it has been a place where a worker without a college degree can secure the middle-class security and comfort that have slipped out of reach elsewhere.

Mr. Lamia and his wife own a home 10 minutes from the foundry, have three cars between them, and a decade ago they purchased a summer place in Michigan’s Upper Peninsula.

In many respects, economic data for the area still paints a sanguine picture. At 2.8 percent, the county’s unemployment rate is more than a full percentage point below the national average. Help-wanted signs hang from local factories, and Neenah Foundry recently raised hourly wages for chippers and grinders, an entry-level job, to about $12.25 an hour from $11.25.

But there is a creeping sense of having to work harder just to stay in place, as salaries and lifestyles erode amid pressure from globalization and the unceasing demand for ever-rising profits in corporate America.

“People are working similar jobs to what their parents did but are not able to maintain the same lifestyle,” said Mark Harris, a former mayor of Oshkosh who is now the Winnebago County executive. “That’s causing anxiety.”

And while unemployment may be low now, older residents have seen factories and mills close in town after town, with Wisconsin losing 120,000 factory jobs over all since 2000, including 20,000 in the paper industry alone. Not only has that kept wages in check, but it has also prompted doubts among blue-collar workers about whether they — or their children — have much of an economic future here.

“We had eight kids in our family, and my mother didn’t have to work,” Mr. Olejnik said. “Grocery stores weren’t open on Sunday and you spent time with your family. Now, the mall is open on Christmas Eve. We’ve lost a lot.”

‘Change Is Hard for People’

Families are always rising and falling in America, Nathaniel Hawthorne observed around the time John Bergstrom’s ancestors arrived in Neenah from Norway 150 years ago, and Mr. Bergstrom can vouch for that.

The first Bergstroms made cast-iron stoves and carriages. When new technologies made those businesses obsolete, they turned to what would become the region’s dominant industry by the mid-20th century: paper.

They prospered, and the Bergstroms joined the other paper barons who built mansions along Lake Winnebago. That house is now a museum, and the Bergstroms’ paper business faded as mills closed.

John Bergstrom, now 71, had the foresight to diversify, moving into automobile sales and then real estate. From a single General Motors dealership that opened in 1982, the Bergstrom family now dominates auto sales throughout the region, selling everything from Chevys and Cadillacs to Hondas, Toyotas and BMWs.

“Change is hard for people,” Mr. Bergstrom said. “So many of the communities in the middle part of America were based on a particular business or industry, and when that changed, the community didn’t. They lost the ability to continue to be what they once were.”

Indeed, as a developer, he helped Neenah avoid the fate of other Midwestern towns that depended on a single smokestack industry.

In 1993, Mr. Bergstrom and 11 other local businessmen each put in $100,000 to develop a decrepit site downtown with a new office building. It quickly filled up — and since then Mr. Bergstrom has helped build seven new office buildings, lifting the work force in downtown Neenah from 500 to more than 3,700.

One of those sites was the former Bergstrom paper mill, which the town tore down about a decade ago. It is now home to the headquarters of Plexus, a rapidly growing maker of complex electronic equipment that also has two manufacturing facilities nearby, employing nearly 2,000 people in all.

“When you fly on a 747, there are likely Plexus parts in that plane that were made here,” said Dean Kaufert, the mayor of Neenah.

There is still a paper mill downtown as well — Neenah Paper, which traces its roots to the 1870s and was spun off from Kimberly-Clark in 2004. The company has thrived by making high-end stationery, labels and other products requiring production and service know-how not easily replicated overseas.

But the closing of so many other mills has a way of obscuring success stories.

Nearly a decade after the mill closed in Kimberly, Wis., putting 570 employees out of work, the town is still struggling with how to redevelop the 91-acre brownfield site.

Last month, the paper maker Appvion filed for bankruptcy, putting at least 1,000 jobs in the Appleton area in jeopardy. Nearby, at Appleton Coated, 500 workers have been laid off since the summer, with a skeleton crew staying on as the company’s new owner seeks a buyer for the plant.

Passing the ruins of the abandoned plant in downtown Kimberly as he drove to work at Appleton Coated every day, Chris Bogan would have the same thought: His mill could be next.

So when that came to pass this fall, after five years of winding massive paper rolls, Mr. Bogan was scared, but not shocked. “Three days after I was hired at Appleton Coated, we were warned about layoffs, so I worried about it all the time,” he said.

Two other local manufacturers did step up and make offers to Mr. Bogan and other laid-off workers, but the $14 to $17 an hour they offered didn’t come close to the $28.66 he was earning at the paper plant.

And with his wife at home taking care of two toddlers, including a 2-year-old son with cerebral palsy, there was no way to bridge that gap. “If my wife was working, that would be acceptable, but in my situation that won’t work,” he said.

A Marine veteran, Mr. Bogan has enrolled at Fox Valley Technical College, and hopes to receive his commercial trucking certification in a few months.

That could lift his salary back above $20 an hour, but in the meantime he and his family are without health insurance. His son’s therapy is covered by Medicaid.

“It’s been a little over a month, and people are coming to terms with the fact that we won’t be making the same wages that we were,” he said. Mr. Bogan said his main concern now was making sure his wife would still be able to bring their son to his occupational, speech and physical-therapy sessions each week.

Downtown Neenah is only a 15-minute drive from his home, but the craft beers on tap there and the farm-to-table restaurants that have opened up might as well be in Madison or Brooklyn.

“The area is changing,” he said. “I grew up on the outskirts of town, and as a local guy, it’s not for me. I’d rather cook a steak at home than go out and pay $120 for a meal.”

‘Go to Where the Fish Are At’

Watching those changes heightens the anxiety at an old-school manufacturer like Neenah Foundry, but these companies and their workers are adapting. Mr. Lamia, the 57-year-old veteran employee who backed Mr. Trump after decades of always voting a straight Democratic ticket, is a case in point.

Although he complains that “it’s so hard to compete against Mexico,” he has reinvented himself more than once during his career at Neenah Foundry.

After his first job as a laborer was eliminated, he got a commercial driving license and drove trucks there. Looking to rise and avoid another layoff from the foundry, Mr. Lamia then spent one day a week for five years at Fox Valley Technical College and eventually became certified as an electrician. With overtime, he earns roughly $70,000 a year, a solidly middle-class wage here.

Indeed, for workers with two-year degrees in fields like automation, metal fabrication and advanced manufacturing, employers are offering $50,000 to $60,000 to start. “We call them gold-collar workers in the state,” said Susan May, the president of Fox Valley Technical College.

But even as salaries for skilled workers like Mr. Lamia have risen, the number of low-paid entry-level laborers at Neenah Foundry is shrinking.

His boss, Tom Riordan, is about to invest $15 million in robots, automating part of the process in which cast metal parts are removed from sand molds by unskilled chippers and grinders.

“American manufacturers need to take a tough-love approach,” he said, sitting in Neenah Foundry’s nondescript board room, not far from the noisy factory floor. “Sometimes you just have to suck it up, adapt, and serve your customers.”

Mr. Lamia favors another sort of tough love: tariffs aimed at the countries he feels are “feeding off the U.S. and don’t play by the same rules.”

To comply with new government regulations, for example, Neenah Foundry will spend more than $1 million over the next six months to reduce silica particles by half, to 25 parts per billion. In China and India, workers simply make do with masks, and Mr. Lamia doesn’t believe he and his colleagues should be at a disadvantage when environmental standards overseas lag behind those in the United States.

“If Neenah Foundry has to pay millions for emissions controls and China doesn’t have to, then they should have to pay more to export to the U.S.,” he said. “It’s got to be a level playing field, and this should have been done a long time ago.”

Mexico is a more complicated case, Mr. Lamia added, especially given the country’s role as a major importer of American grain and other products. “Trump’s got a lot on his plate, but he should impose tariffs on China for sure,” he said.

Appealing as the tough talk on trade might be at times, it wasn’t enough to persuade Mr. Riordan, a self-described moderate Republican, to vote for Mr. Trump. Instead, he cast a write-in ballot for a fellow Wisconsinite, Representative Paul D. Ryan, the House speaker.

Mr. Riordan doesn’t discount the appeal of Mexico to manufacturing executives like himself. But he’s not considering a wholesale move south of the border for Neenah Foundry — instead, he wants to find ways to supply American manufacturers who have relocated there. “A lot of our customers are heading south, and you go where the fish are at,” he said.

As for the Nafta trade deal now being renegotiated, Mr. Riordan favors keeping changes to a minimum, rather than ripping up the 24-year old agreement, as President Trump has threatened to do.

“There isn’t an easy answer, but my personal bias would be against that,” he said. “Let’s put some lipstick on this pig, and not make a whole lot of substantial changes.”

He knows that axles made here will go into vehicles exported to Mexico and other countries that are trade targets of the White House. What’s more, Mexico is a major importer of corn and soybeans from American farmers, who in turn buy tractors and combines from John Deere, a major customer.

“Do we really understand what we’re doing?” Mr. Riordan asked. “We have a big trade surplus with Mexico in terms of grain. If U.S. farmers are suddenly at a disadvantage, who is going to pay the price for that? American agricultural equipment manufacturers, which impacts us.”

As the steward of a manufacturer that has survived world wars, the Great Depression, the Great Recession and a couple of trips to bankruptcy court, Mr. Riordan is much more optimistic about his company’s ability to compete globally than many of his workers.

The same goes for the country’s ability to win in trade with the likes of Mexico or China.

“If rational minds prevail in Washington, over time the country will get it right,” Mr. Riordan said. “But Congress and the president need to get it right in the meantime.”