NILES, OHIO — Representative Tim Ryan won re-election in 2020. But in one sharply personal way, he lost, too.

Mr. Ryan, 48, the Ohio Democrat and one-time presidential candidate, was born and raised in Niles, a manufacturing city of roughly 18,000 that sits halfway between Youngstown and Warren in southern Trumbull County.

Mr. Ryan had once won Trumbull with as much as 74 percent of the vote. That number fell to just 48 percent in 2020, when he narrowly lost the county by roughly one percentage point. A place that was once a bastion of white blue-collar Democrats turned away from a white Democratic native son whose blue-collar grandfather had been a steelworker in Niles for four decades.

Now, Mr. Ryan is trying to win back his party’s voters in Trumbull and throughout Ohio as he runs for Senate. His problem in Trumbull exemplifies the larger problem for Democrats in the Midwest: The lingering appeal of Trumpism and the erosion of support for the party among the white working-class voters who once formed a loyal part of its base in the industrial heart of the country.

Many national Democratic pollsters and pundits have written off Mr. Ryan’s pursuit as a near-impossible task. They see Ohio as too red and too white to change course. But as his Republican opponents have been veering farther to the right and aggressively pursuing former President Donald J. Trump’s endorsement, Mr. Ryan is betting voters have had enough of the extremism in American politics. He is focused on bringing back voters who feel forgotten by Democrats and turned off by Republicans.

“I feel like I am representing the Exhausted Majority,” Mr. Ryan said in an interview, using a phrase coined by researchers to describe the estimated two-thirds of voters who are less polarized and who feel overlooked. People, Mr. Ryan added, “just want to move on and actually focus on the things that are really important.”

Like other Democrats in long-shot races, Mr. Ryan must stay firmly within a narrow lane as he vies to replace Senator Rob Portman, a Republican who is retiring. Mr. Ryan does not tout Medicare for All and other transformative policies that tend to energize progressives, and he does not want to talk about transgender women in sports and other divisive issues. Instead, he wants to campaign strictly on jobs, manufacturing and taking on China. His first television commercial — part of a $3.3 million ad buy — almost sounds like it came from a Republican, squarely centering on the nation’s fight to beat China on manufacturing.

“It’s us versus them,” he says in a digital one-minute version of the ad, during which he mentions “China” eight times in 60 seconds. The ad has drawn criticism from some Asian advocacy groups and elected officials, who described it as racist and called on him to take it down.

Shekar Narasimhan, the chairman of AAPI Victory Fund, a political action committee that mobilizes Asian American and Pacific Islander voters, urged Mr. Ryan to not use hate or fear to win votes. “That’s what the Trump Republicans do and why we fight them everywhere,” he said in a statement.

Mr. Ryan condemned anti-Asian violence but said that he was speaking specifically about government policies of the Chinese Communist Party that have hurt Ohio workers and that he was not backing down.

Seven months before the November election, it is too early to say whether the Ryan playbook is working. Interviews with voters, former elected officials and community leaders in Niles, Warren and other towns in the industrial region known as the Mahoning Valley showed just how hard the midterms will be for Democrats, and for Mr. Ryan. His jobs-and-the-economy message clashes with the prices working-class voters have been paying at the grocery store and at the gas pump.

Many Republican voters in this part of the Mahoning Valley were quick to dismiss any Democrat as unviable, citing gas prices, inflation and the U.S.-Mexico border as Democratic problems that needed Republican solutions. Democrats tended to be split between those who supported Mr. Ryan and those wary he had become too much a part of the Democratic establishment. Even anti-Trump voters have been in an anti-establishment frame of mind.

Outside the Hot Dog Shoppe in Warren, Royce VanDervort, 76, who worked for the Packard electric division at General Motors, said he understood why people grew tired of the Democratic political machine amid factory closures and job losses, but was surprised by just how strong and enduring the Trump appeal has been. He is a die-hard Democrat and said he supports Mr. Ryan. “Too old to change now,” he added.

But Mr. VanDervort’s friend and neighbor, Dennis Garito, 57, was the kind of voter Mr. Ryan has been trying to win back. A retired fabrication worker and a Democrat for 35 years, Mr. Garito now describes himself as an independent. On the one hand, he said, he worries Mr. Ryan and other Democrats have lost touch with the people they represent. On the other, he has grown sick of far-right Republicans who argue, he said, like “kids fighting.”

He plans to vote for Mr. Ryan in the Democratic primary in May. But if an anti-Trump Republican, State Senator Matt Dolan, wins the Republican primary and makes it on the ballot in November, Mr. Ryan will likely lose Mr. Garito’s vote. “If it comes down between Dolan and Ryan, I’m probably going to vote for Dolan,” Mr. Garito said. Mr. Ryan, he added, had become “too much of a career politician.”

Asked later about Mr. Garito’s comments, Mr. Ryan said Mr. Garito reflected those voters in the middle who are without a home politically. His role model has been Senator Sherrod Brown, the Ohio Democrat who has weathered Republican waves by focusing on rebuilding the middle class.

“I am telling everyone right now — ‘Just hear us out, come listen to us,’” the congressman said.

On a blustery, snowy day in early spring, Mr. Ryan sat in Giuseppe’s Italian Market, one of his favorite Italian delis in Niles, dressed down in jeans and a gray pullover with a United Steelworkers logo. In the Democratic primary, Mr. Ryan is the front-runner, but he will face Morgan Harper, a progressive lawyer, and Traci Johnson, a tech executive.

Mr. Ryan has been on a rigorous tour of the state, aiming to visit with voters in all 88 counties. So far, he has hit 82. He met with union workers in town halls, diners and factories along the Ohio River. He hosted round tables with business owners and home health care aides in Cincinnati, Cleveland and other cities. He picketed with aerospace workers north of Dayton.

“I want to see these folks,” Mr. Ryan said. “I want to be in their communities.”

Mr. Ryan’s visit-every-county tactic echoes Beto O’Rourke’s driving tour of Texas in 2017 and 2018, when Mr. O’Rourke made campaign stops in all 254 counties in Texas during his unsuccessful bid to defeat Senator Ted Cruz.

The Mahoning Valley where Mr. Ryan still lives stretches across northeastern Ohio and northwestern Pennsylvania, and was once a thriving zone of steel factories and manufacturing plants. But Mr. Ryan saw the region transform amid job losses, bad trade deals and disinvestment, he said.

“Growing up, you think it is just happening here, but when you travel Ohio, you realize that it is the vast majority of Ohio,” he said.

The exodus of white blue-collar voters from the Democratic Party accelerated here with the arrival of Mr. Trump, who stirred populist anger as he pledged to bring back manufacturing jobs and companies, as well as to aid struggling workers who had been laid off or reassigned. Many of his promises never materialized, but that didn’t hurt the former president’s well of support among the workers who saw him as their champion. Ohio went to Mr. Trump in the past two presidential elections, and it appears to be trending in Republicans’ favor, as President Biden’s low approval ratings are expected to hurt Democrats.

The diminishing support for Mr. Ryan in 2020 in Trumbull County was part of a larger wave of enthusiasm for Mr. Trump that knocked out other well-known Democrats in the Mahoning Valley, said Bill Padisak, who works in Niles and serves as president of the A.F.L.-C.I.O. Central Labor Council in Mahoning and Trumbull Counties. But he said it was too early to tell whether many of those people would remain Republicans.

“A lot of the union members I talk to, I think they will swing back,” Mr. Padisak said.

Democrats’ struggles go far beyond Mr. Trump. The outrage, racial resentment and white grievances harnessed by Republicans have proven too salient for some voters who see their identity and way of life under attack. Others blame the Biden administration and Democrats for the troubles with the economy and illegal immigration.

On a visit to Warren for her 18-year-old daughter’s dance competition, Kristen Moll, 54, echoed a common refrain among Republicans. “Right now, regardless of if you’re running for Senate or governor or any public office, I would feel the Democratic Party in general is leading the country down the wrong path,” Ms. Moll said.

At her home, Charlene W. Allen, 76, a community activist and legislative aide to the Youngstown Warren Black Caucus, believed Mr. Ryan had a shot. But she said he could not win the seat without doing more to repel Republicans’ attempts to sow division, like proactively taking on issues of race and crime.

“Some of that Trump support has waned, but I don’t know if it has waned enough,” she said.

David and Jennifer Raspanti, who are the owners of a painting company in Trumbull County and who are Republicans, said they did not care whether the next senator was a Republican or a Democrat as long as the candidate was not extreme and could make clearheaded decisions.

“We need to come back to the middle,” Ms. Raspanti, 44, said at a restaurant in Boardman Township, where the family was having breakfast with their two sons after church. “We need to listen to each other better.”