WASHINGTON When it comes to illegal immigration, Republican presidential candidates are railing like it's 1999.

Listening to the GOP White House aspirants, you wouldn't know that the number of illegal immigrants in the United States is down, attempted border crossings are at a 40-year low and President Barack Obama has deported undocumented workers at twice the rate of his predecessor.

The issue will likely heat up in the next two weeks as the White House aspirants campaign to win South Carolina's first-in-the-South GOP primary Jan. 21.

With slight variations, the top candidates back mass deportations, tough state enforcement laws and extending the 675-mile fence along the U.S.-Mexico border, and they oppose giving most illegal immigrants a path to legal residency.

"Border crossings are at a historic low, deportations are at a historic high, yet every Republican presidential candidate says the first thing we have to do is secure the border," said Frank Sharry, executive director of America's Voice, a Washington group that wants immigration enforcement to focus on serious criminals and national security threats.

Illegal immigration has long been a hot-button topic in South Carolina, where Sen. Jim DeMint was lionized among Republican activists for his leading role in killing 2007 reform legislation he branded as amnesty.

Conservative radio commentator Rush Limbaugh mocked Sen. Lindsey Graham as "Senator Grahamnesty" for his efforts to pass the measure, and the Seneca Republican has since adopted harder positions on illegal immigration.

Now, a federal judge has blocked a S.C. immigration-enforcement law that was to have taken effect Jan. 1.

Sharry, other pro-immigration advocates and Hispanic lawmakers criticized former Massachusetts Gov. Mitt Romney last week for vowing to, as president, veto the Dream Act, a bill that would provide legal residency to illegal immigrants who attend college, serve in the military and entered the country before the age of 16.

Charlie Black, a native of North Carolina and prominent GOP consultant who ran President Ronald Reagan's winning 1980 campaign, is advising Romney.

Black acknowledged that Romney's hard-line immigration stance runs counter to Reagan, who granted the nation's last broad amnesty, and to Black's support for comprehensive reforms providing a path to legal residency.

"That's the right thing to do, but I'm not running for president and Romney is," Black told McClatchy. " ... I support him."

Other influential Republicans have warned about reversing the inroads Reagan, President George W. Bush and 2008 GOP nominee John McCain made among Hispanics, the country's fastest-growing demographic group with 21.7 million eligible voters - almost three times the 7.7 million in 1988.

"The Republican Party has to discuss (immigration) in as humane a way as possible," McCain told CNN last month. "We have to have empathy, we have to have concern and we have to have a plan."

Former Bush adviser Karl Rove and former House Republican leader Dick Armey have also warned against alienating Hispanics. Their advice has not been heeded.

Former U.S. Sen. Rick Santorum's calls for mass deportations and opposition to any leniency helped him in Iowa, where he came within eight votes of defeating Romney in the Jan. 3 GOP presidential caucuses.

Romney and other rivals pilloried former House Speaker Newt Gingrich for saying in a November debate that undocumented workers who've been in the country for decades should be given a chance to gain legal status.

Under attack, Gingrich issued an "immigration fact sheet" detailing his past tough stances. He flew to South Carolina and declared his support for the state's beefed-up enforcement law, now enjoined by a federal judge.

An MSNBC poll last month of likely voters in S.C.'s presidential primary showed them split over a key issue, with 46 percent backing and 48 opposing "limited amnesty for some illegal immigrants."

Hispanic lawmakers and advocates find irony in the claims by Romney, Santorum and other Republicans that Obama has been soft on illegal immigration.

The federal government deported a record 395,000 foreigners in 2009, and 387,000 in 2010, compared with 189,000 in 2001 and 165,000 in 2002 - Bush's first two years in office.

The number of illegal immigrants in the United States has dropped to 11.2 million from its peak of 12 million in 2007, falling in South Carolina from 70,000 to 55,000 in the same period and from 375,000 to 325,000 in North Carolina, according to the Pew Hispanic Center, a Washington policy group.

The number of people apprehended by the U.S. Border Patrol while trying to enter the country illegally plummeted to 340,000 last year, one-fifth its peak of nearly 1.7 million in 2000.

S.C. Sen. Larry Grooms, the author of the state immigration now enjoined in federal court, declined to credit Obama for stiffened enforcement. He said deportations are up only because enforcement was so lax under Bush.

"President Bush had a terrible policy of enforcing immigration laws," Grooms said. "Republican and Democratic administrations have failed this country."

The Bonneau Republican thinks the drop in the number of illegal immigrants is temporary and will turn around when the economy does.

"It's only a declining problem because of where our national economy stands," he said. "It will become a much larger problem when our economy turns around."

Meanwhile, GOP presidential candidates don't seem to have noticed the decline. Their shrill attacks on illegal immigration, some analysts say, are sabotaging a chance to cut into Obama's political base.

A Pew Hispanic Center survey found widespread anger among Hispanic voters over Obama's deportation levels and his failure to fulfill 2008 campaign promises to pursue comprehensive reforms that would give a path to permanent residency or citizenship to some illegal immigrants.

Yet in the same survey, Obama trounced Romney and Texas Gov. Rick Perry by 3-1 margins among Hispanic voters in head-to-head matchups.

In a remarkable protest by a fellow Democratic lawmaker, Rep. Luis Gutierrez of Illinois was arrested last July when he joined a rally outside the White House against Obama's deportation rate.

Clarissa Martinez will direct get-out-the-vote efforts for the National Council of La Raza, an advocacy group based in Washington. She plans to dispatch door-to-door canvassers to key swing states with large Hispanic populations, among them Florida, Colorado, Nevada, Pennsylvania and North Carolina.

"By being so anti-immigrant, the Republicans are missing a huge opportunity," Martinez said. "They are pushing Latinos towards the Democrats."