Finally, there is a voice of reason on immigration among the front-runners for the Republican nomination, who until last week’s debate seemed to be competing with one another to see who could take the craziest stand against Hispanic immigrants.

Newt Gingrich, the front-runner of the moment as conservative Republicans seek an alternative for ideologically zigzagging second-place contender Mitt Romney, broke with the pack in the Nov. 22 CNN debate of Republican hopefuls by stating an obvious: It is realistically impossible, economically risky and ethically wrong to seek the deportation of all 11.2 million undocumented immigrants in this country.

Gingrich said that ultimately, the United States will have to find a system where, after securing the border with Mexico and launching a guest worker program to fill jobs that Americans won’t take, “you need something like a World War II Selective Service Board that, frankly, reviews the people who are here.”

“If you’ve been here 25 years and you got three kids and two grandkids, you’ve been paying taxes and obeying the law, you belong to a local church, I don’t think we’re going to separate you from your family, uproot you forcefully and kick you out,” Gingrich said.

For people who have been in this country for 25 years, Gingrich offered a “red card” program that would allow them to stay in this country, but not to get citizenship. Others who arrived more recently would be deported, he said.

In addition, Gingrich said, foreigners with graduate degrees in much-needed disciplines would get automatic residency. “I think that we ought to have an H-1 visa that goes with every graduate degree in math, science and engineering so that people stay here,” he said.

Predictably, other Republican hopefuls, trying to position themselves to the right of Gingrich, demanded an all-out deportation of all undocumented immigrants.

Asked by debate moderator Wolf Blitzer where he stands on this, Romney claimed that Gingrich’s red card proposal — a less generous variation of the immigration reform with a path to citizenship plan once supported by former Republican candidate Sen. John McCain in the 2008 elections — is the equivalent of an “amnesty.”

“Look, amnesty is a magnet,” Romney said. “What we have had in the past, programs that have said that if people who come here illegally are going to get to stay illegally for the rest of their life, that’s going to only encourage more people to come here illegally.”

Romney said that “we’ve got to stop illegal immigration. That means turning off the magnets of amnesty, in-state tuition for illegal aliens, employers that knowingly hire people that have come here illegally.”

He added, “We welcome legal immigration. This is a party, this is a party that loves legal immigration. But we have to stop illegal immigration for all the reasons the questioner raised, which is, it is bringing in people who in some cases can be terrorists, in other cases they become burdens on our society.”

Offered a chance for rebuttal, Gingrich said, “I don’t see how the party that says it’s the party of the family is going to adopt an immigration policy which destroys families that have been here a quarter century.”

My opinion: Much of the immigration debate has been dominated by Hispanic-allergic anti-immigration zealots on Fox News and conservative radio talk shows, who get big ratings by bashing Mexican immigrants, and drive Republican presidential hopefuls to echo the same fear-mongering rhetoric.

They rarely mention the fact that the number of undocumented migrants has been declining steadily since the 2008 U.S. economic crisis. Or that the Obama administration — which supports a much more reasonable immigration reform that would include a path to citizenship to long-time lawful immigrants — has deported a record of nearly 400,000 people this year.

Romney’s argument that he is for “legal immigration” is misleading: There is currently virtually no path to “legal immigration.”

A recent study by the National Foundation for American Policy found that it can take up to 70 years for a highly skilled Indian national to receive a U.S. green card. And for many unskilled Mexican workers, the process is so cumbersome and restricted that it virtually invites them to enter the United States through the back door.

What’s needed is updating immigration laws to make them economically advantageous and socially practical. Gingrich’s proposal, while limited in scope, at least brings some rationality to the debate among Republican hopefuls.

— Andres Oppenheimer is a Latin America correspondent for the Miami Herald.