COLUMBIA, S.C. – South Carolina’s Democratic Party chairman says his state’s open primary system is under attack from conservative activists.

What Trav Robertson’s talking about is an effort by some on the right to urge fellow Republicans to vote in Saturday’s Democratic presidential primary in the Palmetto State for populist Sen. Bernie Sanders of Vermont, the current front-runner in the nomination race.

THE LATEST FROM FOX NEWS ON THE 2020 PRESIDENTIAL CAMPAIGN

Those votes could hurt former Vice President Joe Biden – who’s banking on a win in South Carolina thanks to his strong support among the state’s African-American voters. After disappointing fourth- and fifth-place finishes in Iowa’s caucuses and New Hampshire’s primary before a distant second-place showing in last weekend’s Nevada caucuses, the former vice president’s hoping a win in the Palmetto State will resuscitate his wavering Democratic nomination bid.

South Carolina doesn’t register voters by political parties and holds open primaries – which means anyone of any political affiliation or no affiliation at all -- can cast a ballot. With no Republican primary this time around, many Republicans who’ve long argued against open primaries may cross over and vote in the Democratic contest as an act of protest.

“I sincerely believe it’s an attempt for them to try and close the primary system in South Carolina,” Robertson told reporters on Thursday.

But the Democratic chairman also argued predicted that some Republicans will take part in the Democratic primary as an act of protest against President Trump.

“We are an open primary state, and I believe you’re going to have a significant number of moderate Republicans who will vote in our primary because they simply can’t take Donald Trump anymore. They can’t take the behavior, they can’t take the immoral anti-Christian behavior of Donald Trump. They need a change,” Robertson forecasted.

But some conservative activists behind the so-called Operation Chaos 2020 say they’re hoping to help Trump in November by giving their support in February to Sanders – a self-described democratic socialist who they see as a weak general election challenger to the president.

"We are calling for specifically for Republicans and Trump supporters all across South Carolina to turn out and vote for Sen. Bernie Sanders in the Democratic primary on Saturday," conservative activist Stephen Brown told TV station WYFF.

There's speculation Trump himself may urge supporters to vote in Saturday's Democratic primary when he holds a primary eve rally on Friday night in North Charleston, South Carolina.

Bloomberg’s Super Tuesday sprint

Mike Bloomberg on Thursday kicked off a hectic six days of campaigning through Super Tuesday. The former New York City mayor started Thursday in Texas – his sixth trip to the state since launching his presidential campaign. Texas is the second largest state to vote on March 3, when roughly a third of all delegates at stake for the nomination will be up for grabs.

Even before he announced his candidacy, Bloomberg said he would skip the early voting states of Iowa, New Hampshire, Nevada, and South Carolina and instead concentrate on the delegate-rich states that hold contests on Super Tuesday and beyond. And according to the ad-tracking firm Advertising Analytics, the multibillionaire business and media mogul’s spent more than $180 million to flood the airwaves in all 14 Super Tuesday states with TV spots as well as digital ads.

“If you think this campaign is expensive just imagine what four more years of Trump will cost us,” Bloomberg told the crowd in Houston, Texas. Later Thursday Bloomberg campaigned in Oklahoma and Arkansas.

Bloomberg’s itinerary is a work in progress.

Earlier this week senior Bloomberg campaign adviser Howard Wolfson told reporters, including Fox News’ Kelly Phares, “We think there are several southern states that we can do well in. We're obviously going to go to places where we think we can make a difference by our presence. But I think the schedule is pretty much in flux between now and Tuesday. I mean I think we're going to be consistently looking at data that will inform our travel. We want to be in those places where when we fly into a market we can have the biggest impact.”

Carolina in Sanders' mind

Bloomberg wasn’t the only Democratic presidential contender campaigning in a Super Tuesday states Thursday.

Before holding an evening rally in South Carolina, Sanders held two events in neighboring North Carolina, the third largest of the 14 states to vote on Tuesday.

As Fox News’ Allie Raffa reports, Sanders spoke before some 1,500 people at Winston-Salem State University before marching with students down a hill to an early voting site on the college campus.

Klobuchar and an American idol

Sen. Amy Klobuchar also campaigned in North Carolina on Thursday. As Fox News’ Alex Rego reports, she was joined by entertainer Clay Aiken of "American Idol" fame at a stop in Raleigh.

Earlier this month Aiken dropped his support for former Biden and endorsed the centrist senator from Minnesota.

Later Thursday Klobuchar headlines a Fox News townhall in Raleigh.

Fox News Kelly Phares, Allie Raffa and Alex Rego contributed to this report.