CHARLESTON, S.C. — Few people sound more excited about the prospect of Sen. Bernie Sanders, I-Vt., winning the Democratic nomination than South Carolina Republicans.

"It's the best-case scenario," said Republican state Rep. Nancy Mace, who is running for her party's nomination to challenge freshman Democratic U.S. Rep. Joe Cunningham. "Really, it's the best-case scenario for any Republican on the ballot."

South Carolina's 1st Congressional District, which covers over 100 miles of coast from north of Charleston down to Hilton Head Island, has long been a Republican stronghold. The district voted for Donald Trump by more than 13 points in 2016 and for Mitt Romney by more than 18 points in 2012.

Cunningham, 37, a former ocean engineer and Charleston-based lawyer, won the district by a slim 1.4 percentage points in 2018, becoming the first Democrat to represent the area since the 1970s.

Sanders' rise has many Democrats here worried that Cunningham's seat — the object of one of the most competitive House races in the country — would be even more vulnerable if a democratic socialist were at the top of the party's ticket in November. In conversations with down-ballot Democratic candidates and strategists here, many said they were crossing their fingers in hope that Sanders' momentum would come to a halt in South Carolina's primary this weekend.

"It is certainly a conversation that is happening regularly among Democrats. It's to the point that I think it's influencing who some folks will vote for on Saturday," said Brady Quirk-Garvan, the former chairman of the Charleston County Democratic Party. "There is a deep concern about what a Sanders nomination would mean not just for congressional districts, but down-ballot."

Richard Hricik, a Charleston-based lawyer running to unseat a Republican state senator, said: "I am not going to even speculate about a Bernie Sanders win." Hricik is a supporter of former Vice President Joe Biden.

Antjuan Seawright, a South Carolina Democratic strategist, said "there's always a concern when you're from the South" when asked how democratic socialism would play out in state and local races here. "And there's always the concern that people will try and over-intensify whatever messages will come from the top and try and pinpoint it to the bottom."

Many South Carolina Republicans say that's exactly what they would do if Sanders wins the nomination. The attack ads against Sanders, some strategists say, practically write themselves, and the party would have a field day framing the election in terms of freedom vs. socialism.

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"There's a faction of people here who are really worried about this enthusiasm for socialism," Mace said in an interview. "I know we're calling it 'democratic socialism,' but it's socialism all the same."

That's a worry Cunningham appeared to share, telling The Post and Courier newspaper of Charleston ahead of the primary here Saturday that "South Carolinians don't want socialism."

Cunningham has a difficult balancing act ahead: appealing to moderates without alienating his party's progressive wing. For now, that wing seems to understand his dilemma.

If Bernie Sanders occupies the top spot on the Democratic ticket, Rep. Joe Cunningham will face a tough balancing act in the fall. Meg Kinnard / AP

"Joe's in a district where he has to maintain some sort of resemblance of independence if he wants to get re-elected. But he's a lot better than the alternatives that would replace him if he didn't," said Greg Moore, a retiree from Johns Island who voted early for Sanders and supported Cunningham in 2018.

Tirrell Campbell, 40, a Sanders supporter from Charleston, said: "I don't care for [Cunningham's comments] much. But at least I know the devil I am working with here."

Concerns about Sanders' threat to the House majority extend beyond South Carolina.

Of the 40 House seats Democrats netted in 2018, 31 came from districts that Trump won in 2016. None of those Democrats who flipped seats have endorsed Sanders.

"The surest way to flip those seats back to red is for Sanders to be at the top of the ticket," a freshman Democratic lawmaker said in a telephone interview.

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Even his primary competitors have tried to capitalize on the party's increasing fear that putting Sanders at the top of the ticket would come at a cost.

"If you want to keep the House in Democratic hands, you might want to check with the people who actually turned the House blue," former South Bend, Indiana, Mayor Pete Buttigieg told Sanders during the South Carolina debate Tuesday night. "They are running away from your platform as fast as they possibly can. I want to send those Democrats back to the United States House."

Former New York Mayor Mike Bloomberg had a similar message, arguing that "Bernie will lose to Donald Trump" and that House seats "will all go red." At a campaign stop earlier in the week, Biden joined in the chorus, reminding voters of what was at stake this election: "the House, the Senate."

There is some evidence that Democrats' fears might be overblown.

"While there is less ticket splitting in American politics than there used to be, we do still see voters doing it," said Kyle Kondik, managing editor of Sabato's Crystal Ball, a political website at the University of Virginia Center for Politics. "So even if Sanders does do poorly — and that is far from guaranteed — House Democrats may be able to distance themselves from Sanders, much like many Republicans did from Trump four years ago."

In 2016, as Kondik notes, many thought Trump would badly lose the election and end the Republican majority. Instead, voters showed a willingness to split their tickets, and a handful of House Republicans outperformed him in their districts.

Even some South Carolina Republicans, eager to take back Cunningham's seat, have said having Sanders at the top might not be the gift the party hopes it to be. Cunningham, like many other Democrats who flipped Trump districts in 2018, ran a campaign laser-focused on local issues and portrayed himself as above the partisan fray.

"Conventional wisdom says Bernie Sanders might be bad for down-ballot candidates, but in the case of Joe Cunningham, nominating Sanders allows Cunningham to be independent," said former state GOP Chairman Matt Moore, a Columbia-based Republican strategist.

"There's really no better opportunity for a Democrat to show they are independent. Republicans have to be careful not to lead with their chins," Moore said.