CHARLOTTE — When San Antonio Mayor Julian Castro gave the Democrats’ keynote address here Tuesday, it marked a political milestone for the nation’s Hispanic population.

Hispanics in S.C.

Number of Registered Voters Percent of Registered Voters Percent of PopulationBerkeley 1,362 1.4 6.1Charleston 1,784 0.8 5.4Dorchester 1,105 1.4 4.5South Carolina 27,298 1.0 5.3Sources: State Election Commission (registered voters); U.S. Census Bureau (population)

He became the first Latino to deliver such a speech at a major political party’s national convention.

For Ilia Rivera of Greenville, a Hispanic delegate, it was a moment of joy.

“I am so very happy,” she said just before Castro’s talk. “We’re part of the party, and we recognize that.”

But in South Carolina politics, Hispanics are like the party guest standing alone in the corner, minding his or her own business.

The state has seen a rapid rise in its Hispanic population in the past two decades, but these new residents have not made much of a mark at the ballot box — at least not so far.

While Census figures show the state’s Hispanic population currently tops 5 percent, Hispanics make up only 1 percent of the state’s registered voters.

Prominent Democrats, such as Rivera and other experts, have several theories why.

Some of the population may not be eligible to register to vote, said Karen Kedrowski, head of Winthrop University’s Political Science Department. “Residency is far different from registered and eligible voters,” she said.

State Sen. Vincent Sheheen, D-Camden, said he tried to court Hispanic voters during his 2010 gubernatorial campaign but realized many were not registered. He thinks that will change over time.

“Right now, many are more worried about earning a living and taking care of their kids,” he said, adding that their civic and political involvement will follow.

Rivera also said she has spoken with many Hispanic voters who are wary of becoming too politically active, partly because they are familiar with political corruption and retribution in their home countries.

“They are very scared to participate in politics,” she said. “They say, ‘Yes, I am going to vote for Obama, but I don’t want to get involved in anything political.’ ”

Kedrowski noted the Hispanic vote is not a monolithic bloc. Cuban Americans often lean more toward the GOP, while those whose roots are in Mexico and Central America may be trending Democratic, particularly because they’re motivated particularly by issues related to immigration.

The Republicans’ tough talk of building a fence and cracking down on illegal immigrants may drive more Hispanic voters into the camp of Democrats, who have struck a more conciliatory tone on immigration.

Rivera, who was born in Puerto Rico, served in the U.S. Army and moved to Greenville 12 years ago, said she has been frustrated by the nation’s inability to resolve its immigration mess. “The legal route (to immigrate) is not working, period,” she said. “Not working for anyone.”

The low registration and participation rate among Hispanics and Latinos in South Carolina means that there have been few, if any, to hold elected office. Rivera noted that Democrat Ines Alvarez ran for the District 28 State House seat in Greenville County two years ago but lost by a 2-1 ratio to Republican Eric Bedingfield.

Both President Barack Obama and GOP nominee Mitt Romney are pulling out the stops to court the Hispanic vote nationally, particularly because it could make a difference in swing states, such as Florida and Virginia.

It remains to be seen when South Carolina’s Latino bloc will grow to the point where it merits similar attention among candidates here.

Rivera said she knows many Hispanic residents who have left the state after it passed a strict immigration-reform bill last year.

Despite that, both Republicans and Democrats have predicted Hispanic voters will continue to grow in numbers and importance in South Carolina until they become a recognized political force.

“I think you’ll see that over the next few years,” S.C. Democratic Chairman Dick Harpootlian said. “We’re not there yet, but we will be.”

Reach Robert Behre at 937-5771.