WEDDINGTON, N.C. — The last, lingering piece of the 2018 election is about to preview the fundamental dynamic shaping the fight for the White House in 2020.

Tuesday’s do-over election for a congressional seat marred by allegations of fraud last year, taking place in a Republican-leaning slice of North Carolina, exemplifies the key push-pull of politics in the Trump era: Cities and suburbs racing away from the GOP and toward Democrats — and rural and exurban voters roaring back in the other direction, propelled by President Donald Trump’s appeal.

The battle to maximize those trends will shape the 2020 campaign between Trump and his Democratic opponent in virtually every important swing state, from the Midwestern battlegrounds of Michigan, Pennsylvania and Wisconsin to Florida and Arizona in the Sun Belt. And it’s driving the election in North Carolina’s 9th District, which Trump carried handily in 2016 but became a surprising 2018 swing seat amid broad suburban backlash to the president.

The president will hold a rally for Republican nominee Dan Bishop on Monday night in Fayetteville, seeking to boost GOP turnout on one end of the district and outdo Charlotte and its immediate suburbs on the opposite end, where Democrats in Mecklenburg County are in ascendance.

Both Bishop and Democrat Dan McCready hail from Charlotte, giving them a close-up look at the demographic realignment of the Trump era. Bishop, a state senator, was one of just a few local Republicans to survive the Democratic wave election in 2018.

“Obviously, Mecklenburg has changed,” Bishop said in an interview. “It’s a bluer area in its entirety, even my [state] Senate district. So it’s a little tougher there, and the president may have more headwinds there.”

The toss-up race between Bishop and McCready is already the second-most expensive special election for a House seat in U.S. history. And the GOP is going all-out to keep the seat, which has been held by Republicans since the 1960s, in the party’s hands: Between House Republicans’ official campaign arm and the top pro-GOP super PAC, Republicans have boosted Bishop with more than $5 million in outside spending.

In line with the district’s historical GOP lean, McCready is campaigning as a bipartisan candidate who will put “country over party.” He opposes congressional efforts to impeach Trump but says the president should defeated at the ballot box next year.

His campaign has emphasized health care as the top issue, citing Bishop’s votes in the state legislature against curbing prescription drug costs and opposition to Medicaid expansion.

Still, especially in his efforts to connect with rural voters, McCready echoes some of the president’s positions.

“The first thing to understand about folks east of Charlotte is their communities have been devastated by the trade deals out of Washington — perpetrated by both parties,” he said in an interview in his South Charlotte campaign office. “The textile jobs are largely gone. The main streets that used to be bustling at lunchtime 30, 40 years ago — many of them sit empty now. What you’ve got to understand is that people feel that politicians in both parties have let them down, and they’re right.”

Bishop is campaigning as an ardent supporter of Trump and his agenda. In his interview here, Bishop described “an unrelenting trifecta of opposition” to Trump as president from Democrats, the news media “and even official law enforcement and intelligence agencies.”

Asked about his first priorities in Washington should he win Tuesday, Bishop suggested he would join the ranks of Trump’s most outspoken attack dogs in Congress. “I think defending the president — and being vocal about that — will be a role I intend to take immediately,” he said.

Bishop is also leaning on some of Trump’s core issues, particularly the still-growing economy and immigration. He’s seeking to yoke McCready to prominent Democrats — in the interview, he name-dropped presidential candidates Elizabeth Warren and Beto O’Rourke, Rep. Adam Schiff, Speaker Nancy Pelosi and actress Debra Messing — and Bishop is running a TV ad critical of the Mecklenburg County sheriff, who is refusing to work with federal immigration authorities.

Public and private polls show the two candidates running neck-and-neck ahead of Election Day. That’s despite the fact that Trump carried the seat in 2016 by 12 percentage points.

But the winds quickly shifted ahead of the 2018 midterm elections. Last November, Republican pastor Mark Harris appeared to survive the Democratic wave, edging McCready by 905 votes. But credible allegations of absentee ballot fraud in Bladen County linked to Harris’ campaign led the state board of elections to throw out the result and order a new election.

McCready, a first-time candidate and Marine combat veteran, won the Mecklenburg part of the district by 10 percentage points, despite Trump’s 3-point win there two years earlier. McCready also carried five of the other six counties that comprise the district — which, while rural, also contain significant African-American and Native American populations that boost Democrats.

But McCready also lost Union County, a big Republican stronghold just across the interstate that rings Charlotte, by a whopping 20 points.

“If you had to pick one district in the state that was the most honest cross-section of the state, it would be this one,” said Jeff Jackson, a Democratic state senator from Charlotte. “It’s got urban, suburban, exurban and rural. But it’s also got other layers of things that are distinctly North Carolinian: It’s got a major military population. It’s got one of the nation’s largest banking centers.”

Asked what Republicans can do to reverse their losses in cities and metro areas, Bishop said he thinks voters may eventually come back into the fold as cities change.

“Look at San Francisco. I mean, I see things on TV every day,” said Bishop. “It’s a fabulous place, but you have endless encampments of people on the street, and people defecating and urinating on the street, and drug[s] and needles. I mean, just a lot of stuff that you wouldn’t expect to happen in a place that otherwise is known for affluence. And I don’t want to see that kind of thing happen to Charlotte.”

Bishop will join Trump Monday night for the rally in Fayetteville, a military-oriented community anchored by nearby Fort Bragg, where Bishop could benefit from a late Trump-driven turnout boost.

“Right now with the absentee voting, Cumberland [County] is running behind where it was in November of 2018,” said Michael Bitzer, a political science professor at Catawba College who has analyzed the early voting numbers. “A rural county, primarily military oriented with the bases — that seems fit for a Trump rally.”

While Trump will be in Fayetteville Monday, Vice President Mike Pence will stump for Bishop in the more suburban Union County earlier in the day.

“I really like having the vice president doing a noontime event and the president doing an evening event,” said Michael Whatley, the state GOP chairman. “It doesn’t really matter so much where they’re going to be. I think they’re both going to be big draws.”

Both candidates say the 2018 controversy that prompted the re-do election is not a major factor for voters. But both think it could help them on the margins of a close election.

“All those votes were cast, and almost every one of them was a bona fide vote. And they were cast aside,” Bishop said. “That’s a loss that can’t be overstated. I know there are people who are resentful of the fact that their votes were cast aside.”

McCready, on the other hand, describes the do-over as a chance for voters to get “justice.” Asked about the end of what has been a 27-month campaign for the office, McCready said the scandal had motivated him to keep running.

“It’s in God’s hands now,” McCready said. “This, for me, was a calling from the beginning. I was ready to go back to my four little kids and my clean-energy business after the race last time. But when we saw them steal people’s most sacred right — the right to vote — I fought back because it was the right thing to do.”