HARRISBURG — Marsha Mills swings back and forth in presidential elections, supporting both George W. Bush and Barack Obama in the past. In 2016, she was so disgusted by her options that she wrote in Michelle Obama’s name. But in the years since, her anger at President Donald Trump has grown.

“I will be voting for anybody over Trump,” said Mills, 54, a server here in Pennsylvania’s capital city, one of the biggest between Philadelphia and Pittsburgh. “I believe that he is always looking at things to benefit himself, not our country. I think he makes us all look like a bunch of clowns."

Just up the Susquehanna River, about 20 miles north in the rural northern end of Dauphin County, Gary Snyder is ready to vote for Trump again. Snyder once voted for Obama, too, but became disillusioned by what he saw as inaction and a lack of accomplishments during his presidency. Trump is a politician he feels connected to.

“Trump speaks to the working man,” said Snyder, 65, a retired state equipment manager in Halifax Township. “I wish he’d stayed off Twitter from day one; he’d have been better off. But he has reached out to the working people, he’s held to his promises to create jobs, and the economy is going great."

Mills and Snyder represent the sharpening urban-rural divide in Dauphin County, where Trump will hold a “Keep America Great” campaign rally in Hershey on Tuesday. Like much of Pennsylvania — and the country writ large — the urban and suburban areas of Dauphin have moved steadily to the left, while rural areas have become more conservative. This November, that meant sweeping gains for Democrats in the Philadelphia suburbs, even as they suffered steep losses in southwest Pennsylvania and other rural areas.

The political divergence in Pennsylvania has clarified the challenge for Trump and his eventual Democratic opponent: Trump will almost surely lose populous urban areas and their surrounding suburbs by wide margins, and the Democratic nominee will conversely lose big in rural areas. Just how big those margins are will ultimately decide who wins Pennsylvania’s critical 20 Electoral College votes. Trump won the state by less than one percentage point in 2016.

“The suburban problem for Republicans is not confined just to the major metropolitan areas,” said former U.S. Rep. Charlie Dent, a moderate Lehigh Valley Republican and Trump critic who retired from Congress last year.

“Dauphin County is a swing county in Pennsylvania now,” said Christopher Nicholas, a Republican consultant based in Harrisburg. "There has been no breakthrough yet, but smart Democrats know that central Pennsylvania… is fertile ground.”

Dauphin County is hardly a Democratic stronghold. Charlie Gerow, a Harrisburg-based GOP strategist and state party official, cautioned that the Republican base is as motivated and enthused to defend Trump as his opponents are to beat him.

“I don’t think Dauphin County will go anywhere like what you’ve seen in suburban Philadelphia,” Gerow said. “Anyone who views it that way, I would say it’s probably fool’s gold. Central Pennsylvania is going to go very, very strong for Trump. And Democrats are energized now, but for the last 20 years, they haven’t really been in the game.”

Dauphin County voted for both Hillary Clinton and for Republican U.S. Sen. Pat Toomey in 2016. In local races, voters often back Republicans: They again gave Republicans majority control of the three-member board of commissioners last month. Republicans also swept other local races in Dauphin.

With a population of about 276,000, according to a 2017 Census Bureau estimate, Dauphin County is about 100 miles west of Philadelphia, reached by highways dotted with signs imploring motorists to “Keep Christ in Christmas.”

Bush won the county in 2000 and 2004, but Dauphin has voted Democratic in the three presidential races since then.

The area’s 10th congressional district race was closer than anticipated in 2018, with Republican U.S. Rep. Scott Perry edging out Democratic challenger George Scott by fewer than three percentage points after the state Supreme Court redrew the district lines and made it more friendly turf for Democrats. Perry is expected to face a stiff challenge again next year.

Hershey, the site of Trump’s rally Tuesday, is a “classic Republican upscale suburb,” Dent said, with a medical center, the chocolate factory, and more. It’s the kind of place that, like Chester County in the Philadelphia suburbs, had been trending blue for years. Trump accelerated that shift, Dent said.

Given that it’s home to Harrisburg, Dent said, Republicans who succeed in the county tend to be more pragmatic, with a less caustic view of government than some in the modern GOP.

“These are a lot of what I would call ‘governing Republicans’ out there," said Dent, who used to represent part of Dauphin County. "They understand state government, their constituents work in state government, many of them, so there’s an understanding of it. They always struck me as very pragmatic people.”

Amir George, 46, an Egyptian immigrant who owns two Harrisburg restaurants, voted for Obama in 2008 but stopped supporting him by 2012. George largely blamed what he described as Obama’s weak stance on immigration. He voted for Trump in 2016 and plans to do so again.

“I got sick of politicians just giving promises,” said George, who became a U.S. citizen more than a decade ago. “Donald Trump, he protects this country, the good people here, by closing the border. He’s honest, he’s not hiding something. He’s going to say what he believes."

And he touted the strong economy. “Most people I know who own businesses, they support Donald Trump, too,” George said.

Outside Harrisburg, Democratic voters are harder to come by in Dauphin County. Dorothy and Brydon Lidle, of the 900-person Halifax Borough, said they’ve been two of only a small number of left-leaning voters to live there over the course of four decades.

The couple has worked for years on voting issues. Dorothy, 75, is the borough judge of elections, Brydon is a former mayor, and both went door to door as volunteers to register voters. Most of their friends and neighbors are Republicans, though they said politics has become a more fraught topic in recent years.

“It’s to the point where you can’t have a civil discussion with someone who’s your friend, and that’s a shame,” said Brydon Lidle, 77. “Because I used to thrive on political discussions.”

And they’re certainly not as liberal as some voters in Philadelphia and its suburbs: Dorothy likes Mayor Pete Buttigieg of South Bend, Ind., in the Democratic primary. Brydon likes former Vice President Joe Biden, “but I don’t think we need another septuagenarian in the White House.”

“There’s no ‘blue wave’ here,” Brydon Lidle said. “I would love to have one. But if anything it’s more dug in for the Republicans.”