COLUMBIA — A group of prominent Upstate Republicans is preparing to launch a wide-scale effort this week to encourage GOP voters across South Carolina to vote for U.S. Sen. Bernie Sanders in the Feb. 29 Democratic primary, The Post and Courier has learned.

The Republican plan to impact the Democratic race, emerging just weeks before the "First in the South" primary, has two goals: Boost the candidate who the Republicans believe presents the weakest general election threat to President Donald Trump and pressure Democrats to support closing state primaries in the future.

South Carolina has open primaries, meaning voters do not have to register by party and can participate in either party's contest. But some conservative activists have long pushed to change that, arguing it would ensure a more pure party process, and they are hoping this effort will win over Democrats to that cause.

The S.C. GOP executive committee voted last year to forgo its 2020 presidential primary, so the Democratic election will be the only one held Feb. 29.

Greenville GOP chairman Nate Leupp, Spartanburg GOP chairman Curtis Smith, Anderson GOP chairwoman Cheryl Cuthrell and the leaders of multiple tea party activist groups in the Upstate are behind the effort to undermine the Democratic race, with other officials still considering joining them.

The group is set to formally announce its plans at a news conference at the Greenville GOP headquarters on Thursday morning, at which point they intend to spread the message across Republican social media pages in South Carolina and push it on conservative talk radio shows.

"Bernie Sanders is the most socialistic, liberal candidate running in the Democratic presidential preference primary," Leupp told The Post and Courier. "So we feel we can make a strong point that our Democratic state legislators need to help work to close our primaries so it protects them as well as the Republican brand."

The idea is inspired in part by conservative radio host Rush Limbaugh's "Operation Chaos" in 2008, when he encouraged Republicans to vote for Hillary Clinton over Barack Obama in the Democratic primaries in order to keep her in the race and sow division among Democrats.

The most recent Post and Courier-Change Research poll of likely Democratic primary voters in South Carolina had Sanders down by just 5 percentage points against former Vice President Joe Biden, who has long been the front-runner in the state.

That led Leupp to believe they could potentially narrow the gap even more if they can persuade even a small fraction of the state's Republican voters to heed their call. In 2016, about 740,000 voters participated in South Carolina's Republican presidential primary, compared to 370,000 in the Democratic primary.

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"I think we can easily affect the outcome," Leupp said. "This is going to catch on like wildfire."

Presidential preference primaries in South Carolina have no write-in option, so the group plans to pitch the effort to Republicans as a way for them to show their support for Trump even without a primary of their own.

"People have been waiting and waiting for 2020 to come along to vote for Trump, and now they can't" because of the cancelled GOP primary, Leupp said. "But they can still help Trump. And it helps the Upstate's cause of registration by party and closed primaries, so it's a win-win for any conservative Republican."

Leupp said he fully expects some Democrats will be angry about their efforts, but he argued that should prompt them to come around to their view on the potential perils of open primaries.

"If they want to complain about it, they should join us in working to close the primaries," Leupp said.

In a statement after the initial online publication of this story, S.C. GOP Executive Director Hope Walker made clear that the broader state Republican Party is not involved in the effort.

"We do not like Democrats meddling in our primaries and we certainly do not encourage the same thing from Republican voters," Walker said.

"While there are some groups and Republican activists that may decide to participate in the open Democratic Presidential Preference Primary on Feb. 29, the South Carolina Republican Party has taken no official stand on this matter nor will it encourage our members to do so," she added.

Jessica Bright, the South Carolina state director for Sanders' campaign, said, "Donald Trump and the Republican establishment have always been afraid to run against Bernie Sanders going back to 2016 and this is more of the same."

"The truth is that Sen. Sanders consistently beats Trump in general election matchup polls," Bright said. "He's the only candidate with more individual donations than Trump and the only candidate with the network of grassroots volunteers it takes to win in November."