On Tuesday, Democrats in South Carolina will pick between a Goldman Sachs executive heavily favored by the state's party establishment and a 26-year-old Army veteran with no experience in elected office. The results say a lot about where Democrats think their opportunities are to take down Republicans.

The primary will decide who vies against the Republican candidate for the seat vacated by former Rep. Mick Mulvaney, now President Trump's director of Office of Management and Budget, in a general election for the state’s Fifth Congressional District on June 20.

On the Republican side, a former speaker of Georgia's House of Representatives and the state's Republican Party chair are largely seen as the leading candidates — though one outside conservative candidate has started running ads attacking her establishment rivals for removing Confederate memorials from state property.

But as Roll Call points out, Democrats actually did better in 2016 in South Carolina's Fifth District than they did in any of the other special election races. And though they did lose that race by 19 points, a Democratic representative held the seat for 29 years before lawmakers redrew its boundaries in 2010.

This is just one of many stories about how Democrats can best use the opportunities handed to them by an unpopular president and a congressional majority that keeps pushing unpopular bills. The winners in special elections like the one in South Carolina — and Georgia and Montana — help Democrats test out their message ahead of the 2018 midterms, when they stand to win big if they can get it right.

Why a 26-year-old long-shot candidate is challenging a Goldman banker

So far, the race has attracted very little attention from the national media — with the special elections in Georgia, Kansas, and Montana drawing far more press and money from outside donors. But in South Carolina, Democrats will chose who they want to lead them into that uphill battle for the seat.

The frontrunner is Archie Parnell, 66, of Sumter, who served as the managing director of Goldman Sachs Hong Kong from 1996 to 2016. Parnell spent 10 years as a tax attorney for Exxon Mobil before that.

"He'll be the smartest candidate," Steve Creech, the former mayor of Sumter, said of Parnell, while adding that the House candidate does not participate in local politics.

But Parnell's CV didn't sound like the right choice for Democrats in the district to Alexis Frank, the 26-year-old who decided to launch her long-shot bid against Parnell after learning he was the choice of local Democratic Party officials. She lists as her key experience serving as a paralegal in the US Army.

"After the election, I reached out to the Democratic Party here and they said they already had a candidate and that they didn't want to have a primary, and I said I'd love to put my support behind him because this is a really important election," Frank said. "Then I found out who he was."

Frank, a biracial mother of two who lives with her husband at an Army base, added that she “was more equipped to speak to people on the level that they need."

“People are looking for something different, and I didn’t think [Parnell] was different enough,” she said.

Members of Frank’s team say they had a similar reaction. Brittany Kelly, a volunteer with the campaign, recalled researching Parnell after local Democrats announced his candidacy, and said the only thing she could find was his LinkedIn page listing his Exxon and Goldman positions. She and a few friends then decided to look for someone else to support, drawing on a group that attended the local Women's March held after Trump's victory.

“Everyone started texting and messaging each other and asking, 'Is this really the guy they told us to trust?’ And, ‘My god, isn't this everything we want to run against?'" Kelly said of Parnell. "They're going by the traditional Democratic playbook, and we've decided that's already caused us a huge number of losses."

A third Democratic candidate, former Marine Les Murphy, entered the race late and has received less attention.

Among the Republicans, Georgia state representative and real estate businessman Ralph Norman Jr. has raised the most money — $614,000, half of which he donated to himself, according to OpenSecrets.

Of the other six Republican candidates in the field, state Rep. Tommy Pope is expected to be Norman’s leading challenger. Then there's Sheri Few, who has released online ads blasting Pope and Norman for voting to take down the Confederate flag from the state Capitol after a white supremacist murdered nine black parishioners at the Emanuel AME Church in Charleston in 2015.

"It's erasing not only Southern heritage but American history. ... Now they're renaming streets and colleges and destroying monuments to Confederate soldiers," Few said in the ad. Her slogan is "Make America America Again," according to the State.

The special elections offer a test run for Democrats

Democrats have viewed the handful of special elections being held this spring and summer as an opportunity to field-test which kind of candidate gives them the best chance to erase Republicans' congressional majority.

Jon Ossoff, a 30-year-old Georgia Democrat and Hill aide, represents one path for the party. Competing in a wealthy Atlanta suburb, Ossoff ran a campaign that minimized economic populism in favor of one that attacked Republicans over Trump’s values and personality. Ossoff failed to clear the 50 percent mark needed to avoid a runoff, but he did win 48 percent of the vote — a big improvement for Democrats in the deeply red district.

Other kinds of Democratic candidates have also shown promising signs of improving the party’s formula. James Thompson, a civil rights attorney and vocal Bernie Sanders supporter, improved Democrats' performance in Kansas's Fourth Congressional District by 20 points in a special election this February — with almost no support from the national Democratic Party. And Rob Quist, the banjo-playing, Sanders-loving populist trying to win an upcoming special election in Montana on May 25, will give us another chance to see if Sanders-style populism can be harnessed by Democrats in conservative territory.

Also coming up for Democrats: a race on June 6 to replace former Rep. Xavier Becerra in California’s 34th Congressional District, a race to replace former Rep. Tom Marino in Pennsylvania’s 10th Congressional District (the special election hasn’t yet been scheduled), and then a special election on August 15 in Alabama to replace former Sen. Jeff Sessions, now the attorney general.

But the Democratic candidates in South Carolina are offering two entirely different possibilities. None of the candidates in the other races have the deep ties to Goldman that Parnell does — a connection that seemed to hurt Hillary Clinton during the presidential but does not appear to bother the host of prominent South Carolina Democrats who have lined up behind Parnell’s candidacy.

But Frank, too, would represent a path for the party that none of the other special elections has presented. In our interview, the young candidate said she was more intimately connected to the grassroots protesters who came out to oppose Trump’s agenda on the streets, and implied that she’d emerged organically from the party ranks in a way that Parnell had not.

That, Frank said, is one reason she thought she’d have a better chance of winning the special election runoff in June. But to find out, she’ll have to get through her own party first on Tuesday.