Jason Williams, and Sharon Coolidge

Cincinnati

PHILADELPHIA - When Mark Munroe arrived at work Wednesday morning, he was greeted by nearly a dozen people lined up waiting to get into his office near Youngstown, Ohio.

"I've never seen a line waiting to get into my office," Munroe, head of the Mahoning County Republican Party, told The Enquirer. The reason? Republican presidential nominee Donald Trump. "They all wanted Trump signs and stickers and wanted to know how they could volunteer," Munroe added.

Hillary Clinton had received the Democratic nomination for president at the party's national convention the previous night, a nomination she is scheduled to accept Thursday. But in typically deep-blue northeast Ohio, Republicans were gathering to work against her, a sign of Trump's popularity.

In 2016, the Mahoning Valley has become an unusual battleground in swing-state Ohio.

Working-class families across the Mahoning Valley have long been looking for a hero, and Trump has promised to bring back their manufacturing jobs. His message worries Democrats, who fear enough of their own will switch their allegiance to cost Clinton the election.

It's no accident Youngstown will be Clinton's first post-convention stop in Ohio on Saturday.

"The Mahoning Valley is ground zero of ground zero," said Dave Betras, chair of the Mahoning County Democratic Party. "If she can’t win the Valley big, I don’t know if she can win the state."

And winning Ohio is crucial to winning the White House: Since 1960, no candidate has become president without the swing-state's electoral votes.

As many as 6,171 Democrats in Mahoning County voted in the Republican primary, Betras told The Enquirer, a high number for an area that has long thumped its chest about having deep pro-union roots.

Overall, including voters who had sat out in the 2014 primary, Mahoning County gained almost 21,000 new registered Republicans this year, Munroe said. That fueled Trump to a 50.6 percent to 37.4 percent victory there over Ohio Gov. John Kasich, who won the state primary.

"Mr. Trump is the first modern Republican candidate that is competitive in the Mahoning Valley, because he will fix bad trade deals and fight for Ohio working families," said Bob Paduchik, Trump's Ohio campaign manager.

Trump won Trumbull County – Mahoning's northern neighbor – with 52.6 percent of the votes. It was the billionaire real estate mogul's biggest margin of victory among the 33 counties he won. Most of those victories took place in a continuous strip of counties spanning from Clermont County east along the Ohio River and north along the West Virginia and Pennsylvania borders.

Four years ago, Obama easily defeated Republican candidate Mitt Romney in both Mahoning and Trumbull counties – garnering over 60 percent of the vote.

But what will happen to Clinton's bid if Trump gains most of the 15,400 votes that Kasich and Ted Cruz combined for in the Mahoning County Republican primary?

"They absolutely should be scared," said Alex Triantafilou, Hamilton County GOP chairman. "That area has lost a lot of jobs, and Trump is speaking to those people in a way that Mitt Romney did not four years ago. We honestly, in good faith, believe Trump is going to win Ohio for that reason."

Trump's message could resonate in some parts of Ohio, said Marlon Marshall, Clinton's director of state campaigns. "But his success has been at the expense of others," he said. Clinton will seek to show voters she will focus on the economy's impact on everyone, not just the people at the top, he said.

Economic sentiments motivate many of the voters in the Mahoning Valley. The economy there mostly has reeled ever since Sept. 17, 1977, known in the Youngstown area as "Black Monday." A steelmaker, the Youngstown Sheet & Tube Company, announced it would close a plant, starting the wave of layoffs and factory closures in the area.

By 1982, the Youngstown area's unemployment rate had reached 21 percent. The rate is now at about 6 percent, compared with just under 5 percent nationally.

Still, no politician has restored the economy to the level it once was in the Mahoning Valley. But one – and now maybe two – has galvanized hopes.

In 1981, a tough-talking Democrat from a blue-collar family was elected Mahoning County Sheriff. Jim Traficant gave hope to families who were losing their jobs and homes. He refused to follow court orders to evict people from their foreclosed homes. His popularity surged, and he was elected to Congress in 1984.

In Washington, D.C., the bombastic Traficant called for a tougher immigration policy and was against NAFTA because he believed the North American trade deal led to the outsourcing of thousands of Mahoning Valley manufacturing jobs. He gained a cult-like following, Betras said.

Sound familiar?

"Donald Trump has appealed to the leftover Traficant faction – even though Traficant was a Democrat," Betras said.

Traficant, who died in 2014, ended up being convicted on federal corruption charges and spent seven years in prison.

"Jim Traficant actually gave a (expletive) about people at one time in his career," Betras said. "As sheriff, he went to jail so people wouldn't lose their homes. But Donald Trump rooted for people to lose their homes so he could make more money. We’re going to remind people he is not Jim Traficant. Donald Trump is a capitalist trying to capitalize on people’s fear."

Despite Democrats' efforts, more Democrats could defect to Trump in Mahoning and Trumbull counties and throughout Appalachia, said Kyle Kondik, who wrote "The Bellwether: Why Ohio Picks the President."

But focusing solely on the Mahoning Valley doesn't capture the full picture of the battle for Ohio. Look to central Ohio, Kondik said. Trump may not do as well among Delaware County's wealthy Republican voters as Romney did there in 2012. In March, Trump finished a distant second in Delaware County to Kasich, who won the county with 63.9 percent of the votes.

“The question is: Will Trump do as well as Romney did in rich, educated suburban Ohio?" Kondik said.

Still, Kondik said: “If Trump can improve on Romney in Mahoning and Trumbull counties and hold on to Delaware County, he could win Ohio."

Staff writers Chrissie Thompson and Jessie Balmert contributed.