Paul Sracic chairs the Department of Politics and International Relations at Youngstown State University in Ohio. Follow him at @pasracic . The opinions expressed in this commentary are his own.

(CNN) After the 2012 election, the Republican postmortem concluded that the traditional Republican base of mostly white economic and social conservatives had to be expanded if the GOP was ever to win another victory in the Electoral College. Conventional wisdom was that the Republicans should go after Hispanic voters, in part because many were thought to be conservative on social issues.

Trump, however, went after a different group of social conservatives: "Youngstown voters," or working-class white voters in cities and towns across the Rust Belt.

In the end, these voters were crucial to delivering the Electoral College to Trump last year, making the difference not only in Ohio, but also in Pennsylvania, Michigan and Wisconsin.

They are also important to the President's political future. So it makes sense that, on Tuesday, President Donald Trump will hold a rally in downtown Youngstown.

Youngstown is a city that punches way above its weight in politics. It boasts a population of only about 64,000 people, down nearly 30,000 over the past 30 years. Yet every president in recent memory has paid at least one visit to the northeast Ohio city.

During the campaign, Trump came either to Youngstown , or someplace close by , three times. He followed in the footsteps of President Barack Obama, who first came here during the 2008 campaign, and returned frequently during his presidency. President George W. Bush stopped by in 2004, and President Bill Clinton held a huge rally here during his 1992 campaign -- and then spent July 4 in Youngstown just prior to his 1996 re-election.

So why do all these presidents come to Youngstown? Well, here's what Bill Clinton said in 1996 : "Throughout your history, Youngstown and the Mahoning Valley (Youngstown sits on the Mahoning River) have been at the heart of this nation and its life. When our great steel mills and factories built the world's greatest industrial power, Youngstown led the way. When the forces of democracy joined to defeat fascism and then to defeat communism, Youngstown led the way."

Although factories all over the United States contributed to the war effort, Youngstown serves as a symbol for all of them. As Trump might put it, Youngstown symbolizes when America was great.

Bruce Springsteen's song "Youngstown" described how the town is viewed these days:

Well my daddy come on the Ohio works

When he come home from World War II

Now the yards just scrap and rubble

He said, "Them big boys did what Hitler couldn't do"

Or, as Trump might put it: We're not great anymore.

So, it's not at all surprising that Trump would be popular in Youngstown. Indeed, in the fall of 2016, when a New York Times reporter looked up Joe Marshall Jr., a former Youngstowner whose story -- in part -- inspired the Springsteen ballad, he quickly shared his support for then candidate Trump.

Remember, Youngstown is a symbol. More to the point, the voters attributed to Youngstown actually live in suburbs throughout the Mahoning Valley. The Mahoning Valley includes both Mahoning County, where Youngstown is the county seat, and Trumbull County, directly to the north. The counties tend to vote nearly in lockstep with each other, and both, based on their labor history, were deep blue.

In both 2008 and 2012 , these counties gave Obama slightly over 60% of their votes. But 2016 represented a stunning reversal for the Democrats. Although Hillary Clinton won Mahoning County, she did so by only three points, not even reaching 50% of the vote. Trump actually won Trumbull County with about 51% of the vote. This helped Trump win the Buckeye State by nearly twice the margin that Obama had enjoyed in 2008.

How did he do this? Controlling illegal immigration was certainly part of the message, but when Trump promised to "make America great again," Youngstown voters understood that to mean bringing jobs back to places like their hometown. And the pitch made sense. Talk all you want about bankruptcies and bad business deals, Trump built a high-rise in the middle of Manhattan with his name emblazoned in gold on the side, and jets around the country in a private plane. How are you going to argue that he is not successful at business? And what do successful businesses provide? In a word, jobs.

As a poll released last week by NBC news and the Wall Street Journal shows, Trump remains fairly popular among Youngstown voters. The stories about meetings with Russians during the election really don't resonate at all. These stories are latched onto by those who hate Trump because his election never made sense to them in the first place. Something corrupt must have happened; how else could Trump have, to their minds, fooled so many voters?

Youngstown voters know they didn't vote for Trump because Vladimir Putin wanted them to. They voted for Trump because he promised them jobs, and they believed him. When Trump mentions Youngstown, as he did at the end of his speech withdrawing from the Paris climate agreement, they know he hasn't forgotten them.

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So when Trump arrives to speak in Youngstown on Tuesday, the Democrats will protest outside, but some of their former members will be inside, cheering on the President. Unless they can figure out how to win those voters back, the future is not bright for them in the Youngstowns across the US.

And, unfortunately for the Democrats, there are many of them.