Archie Parnell, right, talks with Washington Ray at the Black Cowboy Festival in Rembert, S.C., on Saturday. Parnell won the Democratic nomination in the state’s 5th District. He is seeking the House seat left open by Republican Mick Mulvaney, who joined President Trump’s administration. (Sean Rayford for The Washington Post)

Archie Parnell arrived at the Black Cowboy Festival with an impossible mission — talking politics to people who had paid $20 apiece to eat barbecue and watch horses gallop around a track. He was the local Democratic nominee for Congress, but he’d never run for office before, and shaking hands did not come naturally.

“I’m running for Congress,” Parnell said to a polite but quiet couple sitting down to split a fried turkey leg. “I’d be grateful if you consider me.”

He shook more hands; he started and halted conversations as a loudspeaker blared the name of the next horses and riders. But after he found a rhythm, he won the vote of Reneth Jones, 59, by talking about the Republicans’ plan to gut the Affordable Care Act.

“Man, when you take that away, people are going to suffer,” Jones said.

“We don’t see any compassion in what they do,” Parnell said. “It was a close vote. If you send me to Washington, I’ll be a vote against that bill.”

Archie Parnell talks with potential voters at the annual Black Cowboy Festival on Saturday. (Sean Rayford for The Washington Post)

Parnell, a 66-year-old tax attorney, had been a candidate for South Carolina’s 5th Congressional District for just two months. The seat had opened when Mick Mulvaney joined President Trump’s administration, and Democrats, bullish on races in Georgia and Montana, had said almost nothing about it. Georgia’s Jon Ossoff had raised more than $10 million for his June 20 runoff; Parnell, whose election is the very same day, had raised less than one-hundreth as much.

In the wake of the House’s health-care vote, Parnell and South Carolina’s beleaguered Democrats are trying to make Republicans sweat in a district that isn’t making it easy: one drawn to elect a Republican, and with a substantial black population that Democrats struggle to turn out.

While Democrats grow bullish on how a suburban “resistance” can roll back Republicans, Parnell is testing whether black voters can be turned out with a warning that a Republican-dominated Congress is threatening the way they live.

But with no air cover from national Democrats, Parnell has tried to turn his scrappiness into an advantage. A former congressional staff member who went on to work for Goldman Sachs, he quickly tells people that he had never sought office until the 2016 election got him thinking — and until his hometown mayor told him he would be a good candidate. He showed up to the Black Cowboy Festival wearing a sweater vest; in campaign material, he is pitched not as a partisan Democrat, but as a “tax expert” who wants to fix the ACA and “broaden the base” for tax reform. His most-aired ad mocks his very ordinariness, showing him striding toward the camera in slow motion before he finally tells the narrator to knock it off.

“He’s the one man who’ll solve all your problems, and bring Clemson and Carolina fans together,” the narrator says.

“Wait, what?” Parnell says. “Politicians promise and then don’t deliver.”

Archie Parnell, left, chats with people attending the Black Cowboy Festival in Rembert, S.C., on Saturday. (Sean Rayford for The Washington Post)

Republicans are skeptical, verging on cocky. Last week, they caught their first bad break in the district when their primary ended in a near-tie between Tommy Pope and Ralph Norman, two conservative state legislators. (Norman sought and lost the 5th District seat 11 years ago.) That kicked off a two-week runoff, forcing the candidates to spend money and keeping the state party neutral until it has a nominee.

“Archie Parnell’s a nice guy, and he’s got two weeks of being ignored,” said Matt Moore, the outgoing chairman of the South Carolina GOP. “But he’s going to have a problem getting Democrats mobilized, while Republicans are excited that the House is keeping its promises. I don’t expect us to pull the fire alarm.”

But South Carolina Democrats like to point to Kansas, where a Democrat lost by 7.2 points in a district the last Republican congressman had won by 31.1 points. A swing that size in South Carolina would elect Parnell.

Pope and Norman, whose campaigns did not respond to repeated questions from The Washington Post, have made no statements whatsoever about the Republicans’ American Health Care Act. In their ads, both candidates pledge to repeal “Obamacare,” and in one spot Pope even invokes the image of the 44th president to say “there’s no justice in Washington.”

The upshot is that both GOP campaigns believe that the 5th District is ripe for whoever wins their primary. Mulvaney, in 2010, was the first Republican ever to win the district, which stretches from the suburbs of Charlotte to the exurbs of Columbia. In 2012, it rejected Barack Obama’s reelection by 12.5 points; in 2016, it voted for Donald Trump by 18.5 points.

Parnell’s theory of victory takes that into consideration, and asks what could be done to change the electorate. One reason that 2012 gave the Democrats a closer race was that 28.1 percent of the district’s residents, and a smaller percentage of its voters, are black. South Carolina Democrats, without overselling their chances, are universal on one point: If Parnell can make the electorate resemble 2012, using health care as an issue, he is in the hunt.

“It’ll take a campaign that concentrates on voter turnout, rather than TV advertising, which is what previous candidates have tried and failed,” said Rep. James E. Clyburn (D-S.C.), the sole Democrat in the state’s delegation.

Some of the Republicans’ Obama-era gains have come when nonwhite voters sat at home. In polling by Priorities USA, a pro-Democratic super PAC, black voters who did not usually vote in midterms remained less likely to express interest in voting next year than angry white liberal voters. According to a new analysis of the 2016 election turnout, the two states that broke most dramatically away from Hillary Clinton — Wisconsin and Michigan — recorded a double-digit decline in black voter turnout.

South Carolina Democrats have responded by telling black voters that they are facing new and direct threats. In a radio spot that helped Parnell win the nomination — over two little-funded black candidates — Columbia’s black Democratic mayor beseeched voters to send Trump a message. “Donald Trump asked us, ‘What did we have to lose?’” Mayor Stephen K. Benjamin asks in the ad. “Now we know the answer.”

This past weekend, as he stumped across black neighborhoods, Parnell did not get many questions about tax policy. He was not challenged on his Goldman Sachs résumé — something Republicans plan to attack to alienate him from liberals. (Parnell plans to rebut them by saying he was not a banker, but a “policeman” for tax compliance.)

Instead, he was egged on to fight Trump. At several homes near his Rock Hill campaign office, he was stopped and invited in so that voters could rant about the president. One retiree rifled around in his pocket for $5, so he could “start a fund to send Trump to Russia.”

On Sunday morning, Parnell was invited to Faith, Hope & Victory Christian Church in Lancaster, shaking hands on the way in before taking a seat in the first pew. “In the old days, I’d have sat over there,” he said, pointing at the back of the room. “I’m really an introvert.”

Halfway through the sermon, between the hymns and an interpretive dance, Parnell introduced himself to the dozens of rapt voters (and phone-checking teenagers) who came every Sunday.

“Can you imagine an America without Social Security?” Parnell asked. “It would be a very different place, a place I don’t want to live in.”

The congregation was polite, but unmoved. Parnell picked up a fan he had been given, covered in pictures of the first black president.

“Can you imagine the world that we’d be living in without Barack Obama?” he asked. Softly, one congregant said “health care” — and Parnell had his cue.

“I’m glad you mentioned that,” he said. “Actually, this past week, the House voted to repeal Obamacare. If I were there, at that time, I would vote against that repeal. One or two votes make all the difference in the world.”