“I don't think you have a heart.”

When Rick Perry issued this rejoinder to those who oppose his program to give the children of illegal immigrants in-state tuition privileges in the Texas university system, his GOP debate opponents (and conservatives generally) jumped all over him.

In addition to his jumbled answers to some questions, it was his low point in the Republican presidential candidates’ debate Thursday night, and it cost him the Florida straw poll two days later. Some tea party activists even suggested that Perry’s attitude on immigration meant it was all over for the man they once saw as their champion to deflect what seemed to be the juggernaut of Mitt Romney – the man many conservatives don’t trust and don’t particularly like.

For his part, Romney quickly picked up on the issue.

“I think if you are opposed to illegal immigration, it doesn’t mean you don’t have a heart. It means you have a heart and a brain,” Mitt Romney said the next day at the Conservative Political Action Conference in Florida.

[For the record, here’s Perry’s full quote: “If you say that we should not educate children who come into our state for no other reason than that they've been brought there through no fault of their own, I don't think you have a heart. We need to be educating these children, because they will become a drag on our society.”]

For Perry, his state’s version of the Obama administration’s “Dream Act” proposal for helping students without legal immigrant status has become like “Romneycare” – a state-specific position that’s hard to justify in the context of today’s national debate on such issues.

But just as health care is for former Massachusetts governor Romney, immigration is a more subtle and complicated issue for a governor whose border with Mexico is more than 1,200 miles long. It’s not as simple as erecting a fence and authorizing local police to enforce federal laws against illegal immigrants (with the racial profiling that might involve).

“Maybe Mitt Romney doesn't realize that many children of illegal aliens aren't illegals themselves. As long as ‘birthright citizenship’ is the law, ‘anchor babies’ are protected under the law as American citizens,” writes conservative columnist and broadcaster Kevin McCullough. “Maybe Mitt Romney doesn't realize that nearly all of the rest of children of illegals, had no choice in whether to live in Texas or not. If they were brought there by parents who were illegal – how is that the child's fault? Is Romney ready to charge those children with crimes? Mass deportations?”

In a way, Perry’s stance is the more “compassionate conservative” one of his predecessor as governor, former president George W. Bush. And it certainly has bipartisan support in Texas, where all but four of 181 state lawmakers voted for the college tuition law Perry signed.

But as James Hohmann wrote this weekend in Politico.com: “The pendulum has swung significantly since then-President George W. Bush passed comprehensive immigration reform and then-Florida Gov. Jeb Bush backed driver’s licenses for undocumented immigrants. Sen. John McCain, for example, took a much harder line on the issue last year than he had during his 2008 presidential campaign to head off a tough primary challenge from former Rep. J.D. Hayworth.”

That puts Perry in a bind regarding one of his key pitches, which is that his policies have helped create jobs in Texas.

“It is true that Texas is one of the only states where the number of people working has increased during the recession. What has not been acknowledged is that immigrants have been the primary beneficiaries of this job growth, not native-born Americans,” the Center for Immigration Studies reported this past week. “About 40 percent job growth went to newly arrived illegal immigrants and another 40 percent to new legal immigrants.”

Meanwhile, according to this report, “The unemployment rate and the employment rate … of natives in Texas show a dramatic deterioration during the recession that is similar to the rest of the country. Among the native-born, Texas ranks 22nd in terms of unemployment and 29th in terms of its employment rate.”

Perry and his supporters argue that the federal government – especially the Obama administration – is at fault for not taking a tougher stand on illegal immigration.

But there’s another reason why immigration is a tough issue for the GOP and not just for Perry.

In the 2008 presidential election, Hispanics voted 2-to-1 for the Obama-Biden ticket over McCain-Palin. Since then, immigration has become an even hotter issue – especially at the state level with Arizona and Georgia enacting tough enforcement laws now being challenged on constitutional grounds.

As the recent GOP presidential debate shows, it’s sure to be argued about right up until the 2012 election.