CHARLESTON, S.C. — Here’s the good news for Mitt Romney in South Carolina: Since 1980, every GOP candidate who won the primary here went on to receive the presidential nomination. And that candidate, despite this state’s conservatism, was always the most mainstream, establishment politician in the race.

That might come as a surprise, given that 30 percent of South Carolina Republicans claim membership in the Tea Party, and 75 percent agree with Tea Party principles, according to a recent Winthrop University poll.

Moreover, those Republicans also say they would prefer to vote for a candidate whose politics more closely align with their beliefs than for a candidate who  they believe has the best chance of beating President Obama.

Voters might say their preference is principle over viability, but the state’s voting record proves otherwise – and the Romney campaign knows it.

“The No. 1 goal is to send Barack Obama home to Chicago,” Romney campaign chairman and South Carolina state treasurer Curtis Loftis told ABC News. “Thirty day ago, conservatives were fighting me on what Romney stands for. Now they’re not. We’ve got to make sure we unite behind one candidate.”

Romney’s strategy for this state, the first primary in the South, is not to quibble about policy, Loftis said, but to remind voters he has the best chance of winning.

“Voting is a clerical decision,” said Loftis, who identifies as a Tea Party Republican. “You’ve got to make a choice. Either you come in first place or dead last. People love the newness of Cain, the spirit of Perry, the genius of Gingrich, but they know Romney is the only one who can win.”

For now, though, Romney continues to trail in the polls behind Herman Cain, although the full impact of  the sexual harassment allegations against Cain is  still unknown.

Cain is playing the opposite game, directly targeting Tea Party Republicans and what they believe.

It’s Cain’s 999 flat tax plan that most speaks to the Tea Party’s opposition to increased taxes and government spending.

“This is the first election  since the rise of the Tea Party,” William Head, Cain’s South Carolina director, told ABC News.

“We have a strong ground game. Across the state we have large numbers of supporters. We don’t have the most money, but we’re getting the message out and the voters are coming to us,” Head said.

Head would not comment directly on the Cain scandal.

“People outside of South Carolina look at South Carolina as monolithic in its conservatism, and see it as Tea Party leaning,” said Scott Huffmon, a political science professor at Winthrop University in Rock Hill, S.C. But the faithful can be won over with a candidate who can deliver a victory,” he said.

The other candidates to the right of Romney are each trying to distinguish themselves, but there’s little that makes them different on policy. Instead they’ve had to resort to jabbing one another and accusations of ideological impurity, said Huffmon.

Former Sen. Rick Santorum has tried to distinguish himself as the evangelical candidate. But, said Huffmon, there’s enough in common with evangelicals and the Tea Party types, that the distinction is less important this cycle.