RUTHFULLY YOURS

“Strangely, in Tuesday evening’s “economic” debate in Hanover, N.H., immigration, legal or otherwise, was never mentioned. Indeed, Messrs. Romney and Cain have demonstrated less interest in illegal immigration itself than in using the issue to attack Mr. Perry. Mr. Romney, whose jobs plan includes no fewer than 59 points, has said of illegal immigration, “Of course we build a fence,” as if that were all there were to it. If the other GOP candidates wish to place themselves to the right of Mr. Perry on this issue, fine. But Republicans would have more faith in their ability to secure the border if they demonstrated that they had given the matter some thought.

Mr. Perry should stop sounding so defensive. He has opposed illegal immigration as stoutly as anyone, but, alone among the candidates, he has dealt with the reality of life on the border. Since his state has the good sense to provide only modest welfare benefits, he should explain, Texans understand that immigrants come to Texas to work, not to collect handouts. And they see no contradiction between calling on the federal government to enforce the law and making the best of the situation Washington has imposed on them, helping undocumented aliens, once in the state, to acquire skills and an education.”

The fight for the Republican presidential nomination has produced a spectacle that seems truly odd. Although illegal immigration has in recent years been drying up—according to a report by the Pew Hispanic Center, it has fallen to 300,000 in 2009 from 850,000 in 2000, while Princeton’s Douglas Massey says that “[f]or the first time in 60 years, the net traffic has gone to zero”—the issue remains bitterly contentious in the GOP race.

During a debate in Orlando last month, Texas Gov. Rick Perry defended his state’s policy of charging undocumented aliens the same tuition at state-run colleges and universities as ordinary citizens—a policy that commanded bipartisan support in the Texas legislature when he signed it into law in 2001. Mitt Romney, Herman Cain and the other GOP presidential candidates practically hissed Mr. Perry off the stage, and after the debate much of the tea party joined plenty of regular Republicans in denouncing the man.If illegal immigration is down, why do Republicans still care so much about it? Permit a Californian to attempt an answer.

Since 1986, when President Reagan signed the Immigration Reform and Control Act, the undocumented population of California has risen to around 2.6 million from around one million. This influx has done just what you would have expected: It has affected every aspect of life in the Golden State.

In California’s public schools, the proportion of children in kindergarten through third grade for whom English represents a second language now stands at almost two out of five. In agricultural regions, entire towns have turned over—with a little zig-zagging, you could hike from town to town for much of the 450-mile length of the Central Valley without hearing any language but Spanish.

Consider one neighborhood in Redwood City, a town on the San Francisco peninsula. Known locally as Little Mexico, the neighborhood, which centers on the intersection of Fifth Avenue and Middlefield Road, looks and feels so pervasively south-of-the-border that if you were led there blindfolded you would think you were in Tijuana or Mexicali.

I assumed when I moved to California almost two decades ago that Little Mexico, which then comprised perhaps a dozen blocks, would gradually shrink or atrophy, like North Beach, the Italian neighborhood in San Francisco, or Little Italy in Manhattan. Instead, Little Mexico has roughly tripled in size. Just miles from the headquarters of Apple, Google, HP and Oracle, the engine of assimilation has been humming ineluctably along—in reverse.

Yes, I know. The economic benefits California has derived from immigration, including illegal immigration, have proven enormous. Some studies even suggest that, taking into account the economic growth their labor has made possible, and the sales taxes and other imposts they have paid, undocumented aliens have contributed more to government coffers than they have drawn down.

And even after the American economy finally recovers, falling poverty and birth rates in Mexico suggest that illegal immigration may return only as a small stream—perhaps even a trickle—and not a flood. Over the next decade or so, many of the aliens now in the Golden State will perhaps go home to a modernizing Mexico while Californians come to accept—or at least become resigned to—those who remain, acquiescing in measures that would grant them legal residency and eventually citizenship.

Yet even if a single alien were never again to enter California, and even if half those now in the Golden State illegally were suddenly to return home while the other half magically became citizens, the federal government would still have permitted millions to enter the state in violation of the law. This raises fundamental questions about our constitutional order. How can the federal government fail for years on end to perform a duty as basic as policing the border?

Strangely, in Tuesday evening’s “economic” debate in Hanover, N.H., immigration, legal or otherwise, was never mentioned. Indeed, Messrs. Romney and Cain have demonstrated less interest in illegal immigration itself than in using the issue to attack Mr. Perry. Mr. Romney, whose jobs plan includes no fewer than 59 points, has said of illegal immigration, “Of course we build a fence,” as if that were all there were to it. If the other GOP candidates wish to place themselves to the right of Mr. Perry on this issue, fine. But Republicans would have more faith in their ability to secure the border if they demonstrated that they had given the matter some thought.

Mr. Perry should stop sounding so defensive. He has opposed illegal immigration as stoutly as anyone, but, alone among the candidates, he has dealt with the reality of life on the border. Since his state has the good sense to provide only modest welfare benefits, he should explain, Texans understand that immigrants come to Texas to work, not to collect handouts. And they see no contradiction between calling on the federal government to enforce the law and making the best of the situation Washington has imposed on them, helping undocumented aliens, once in the state, to acquire skills and an education.

A quarter-century after Reagan signed the Immigration Reform and Control Act, his example remains instructive. Reagan supported one provision of the 1986 act, an amnesty for the three million undocumented aliens then in the country, only because he believed that other provisions, which fortified border enforcement and required employers to verify the legal status of their workers, would end illegal immigration. “Future generations . . . will be thankful,” the president said, “for our efforts to humanely regain control of our borders and thereby preserve one of the most sacred possessions of our people: American citizenship.”

Thankful? Americans instead feel angry—and, for all his big-hearted openness toward immigrants, I believe Reagan would have shared their anger, recognizing the failure of the federal government to “regain control of our borders” as a profound breach of faith. That breach of faith, he would have insisted, must now be repaired.

Mr. Robinson, a former speechwriter for President Ronald Reagan, is a fellow at Stanford University’s Hoover Institution and co-founder of Ricochet.com.