Every day last year, the immigration service apprehended some 1,400 illegal immigrants trying to cross into Arizona. Over 12 months, along the whole southern border, the total number arrested was more than a million. Morgan has seen too much in life to be anything but candid, and although it's his job to help catch these unauthorized migrants, he criticizes the apprehensions as a waste of time and resources. "They're just poor people trying to feed their families," he shrugs. But that doesn't mean he isn't concerned--very concerned. The main issue in his eyes: the distraction the immigrant influx creates. "What if another 9/11 happens and I'm responsible?" he asks. "What if the bastards come across here in Arizona and I don't catch them because I'm so busy chasing a busboy or a gardener that I don't have time to do my job--my real job--catching terrorists? I don't know how I'll live with myself."

Morgan's personal nightmare is one urgent reason why all Americans, no matter what their politics, should support President Bush's plan to retake control of our southern border. The White House proposal, introduced in early 2004 and allowed to drop from sight during the election year, is back on the table. The president laid out his ideas again in the State of the Union and is reportedly planning a major initiative to take the issue to the public later this spring.

Republicans are no less divided this year than last, and the White House has been working overtime to finesse those divisions. In early February it shrewdly avoided a confrontation in the House by backing a package of tough enforcement measures that many had expected would expose a rift between the president and less immigrant-friendly Republicans. Instead, the administration and its allies cast the "REAL ID Act"--the brainchild of powerful Judiciary Committee chairman James Sensenbrenner--as a first step toward the broader reform they seek, helping the measure pass by a healthy margin. But this will hardly end the discord in Republican ranks, and a major showdown is sure to come, both in Congress and, more broadly, among conservatives across the country.

The Bush plan has two key components: a guest worker program and a transitional measure that would allow illegal immigrants already here and working to earn their way onto the right side of the law and participate legally in the U.S. labor market. Conservative critics lambaste both elements, not just as bad policy, but as inherently un-conservative--out of keeping with core principles and detrimental to Republican interests. The impulse behind the challenge is understandable. Conservative criteria are different: not just security, but the rule of law, traditional values, and national cohesion--not to mention the interests of the GOP. It's also true that the president often touts his proposal in terms designed to appeal across the political spectrum. He talks about "compassion" and a desire to reward "goodhearted" workers, and sometimes this emphasis obscures the hardheaded, conservative case for his approach--a case that begins but does not end with America's economic interests. In reality, though, demonized as it has been on the right, the Bush plan meets every conceivable conservative criterion--with flying colors.

THE PRESIDENT'S REPUBLICAN OPPONENTS often put their case as a rhetorical question--"What part of 'illegal' don't you understand?"--and the gibe hits home, not necessarily because of what it says about the Bush solution, but because it so accurately diagnoses what's wrong with the existing system. Our immigration system is indeed based on illegality--on a long-standing and all but deliberate mismatch between the size of our yearly quotas and the actual needs of our labor market, particularly at the lower reaches of the job ladder. This mismatch has often been convenient for employers--it provides a docile, disposable foreign labor force--and it has been the norm in agriculture off and on for nearly a hundred years. But in recent decades, new technologies have spurred demand for low-skilled workers in a wide range of other sectors as well, and the public, quite understandably, is beginning to find the hypocrisy intolerable.

As the president's critics understand, this is a large part of what is driving voters' concerns about immigration. People don't like the idea of 10 to 12 million illegal immigrants living in the United States but outside the law. They're appalled that entire American industries--not just agriculture, but hospitality, food processing, construction--operate on the wrong side of the rules, relying on the black market to find the labor they need just to keep their businesses open. The very idea of this second, illegal America is an affront, its practical consequences even more troubling: not just criminal syndicates that thrive on lawlessness, but also the haven it creates for potential terrorists. And the public is right: If routine illegality is the price of immigration, it's too high a price to pay--even if the newcomers are good for the economy.

So the critics' diagnosis is not far from the mark. But the question is what to do about this other, illegal America--and the fact is that the president has the best idea, arguably the only idea that can possibly work. Many of his critics believe that the answer is to turn off the immigrant influx. We should, they say, make the necessary economic adjustments and do without the imported labor. It's an option; with enough resources, we probably could stop the flow. But are the American people prepared for the changes that would come with that decision? The likely economic sacrifice is incalculable: not just a few extra pennies on the cost of lettuce, but forfeited growth all across the economy, on a vast scale. In many industries today, growth depends on foreign laborers, who filled one in every two new jobs created in recent years. Then there would be the cost of enforcement--a cost in dollars but also in the way we live. Just ask experienced agents like Lee Morgan: Cutting off illegal immigration would require thousands more men on the border, routine sweeps in every city, roadblocks, roundups, massive deportations, a national ID card, and more.

The president has a better solution. He proposes that we face up to the reality of our growing demand for labor, skilled and unskilled. His outline is still just that--an outline--and he is likely to leave it to Congress to fill in the details: to devise a way to match foreign workers with American employers, to make sure American laborers aren't undercut in the process, to design a method for monitoring employers and punishing those who don't comply, and so on. But the White House has nailed down the all-important central principle: If we raise our quotas to make them more commensurate with the existing flow of foreign workers, we can reap the benefits of immigration without the illegality that currently comes with it.

A new, more realistic policy would be much easier to enforce. The best analogy is Prohibition: Unrealistic law is extremely difficult to make stick. Realistic limits are another thing entirely. We can have robust immigration and the rule of law too--if, instead of wishing away the influx, we acknowledge reality, then find a smarter, more practical way to manage it. And that is exactly what the president proposes we do through his guest worker program. The idea is not to expand the total number of immigrants who enter the country each year, merely to provide those who are coming anyway--and would otherwise come illegally--with a safe, orderly, legal route. Assuming it works--assuming, as the White House does, that once most jobs are filled by authorized immigrants, there will be little incentive for others to come illegally--it's a simple, pragmatic solution, and that in itself should recommend it to conservatives.

EVEN MORE IMPORTANT would be the dividends for national security. Hundreds of thousands of foreigners enter the country each year without benefit of background checks or security controls of any kind. Then, once in the United States, they cluster in transient, underground communities, as often as not beyond the reach of the law. The president understands that we must come to grips with these potential terrorist havens, eliminating not just the illegal arrivals but also the illicit population that has accumulated here in recent decades. That's why he has included a provision that would allow unauthorized migrants to come in out of the shadows and get visas. Though mocked as a spineless, soft-hearted giveaway, this part of the plan too is driven by our needs--our security needs.

Under the Bush plan, foreigners seeking to disguise their identities would no longer find fake ID cards readily available on street corners in every American city. The Department of Homeland Security would have a much better grasp of who is here and what their names are and where to look for them if they turn up on an international watch list. Agents like Lee Morgan would be able to get back to their real jobs: tracking criminals and terrorists, not farmhands and busboys. And all this could be achieved without a draconian crackdown of the kind we would need were we to enforce the quotas we have, let alone close the border. Far simpler to bring the law back into line with market reality, then implement the new rules with modest, commonsense enforcement measures of the sort we rely on in every other realm of American life.

But isn't what the critics say true--isn't the president's plan in fact an amnesty? Not necessarily. It depends how it's done. Illegal immigrants should not be forgiven for breaking the rules; they should be offered an opportunity to earn their way back onto the right side of the law. Think of it as probation--that all-American idea, a second chance. The president is unequivocal: Unauthorized workers will not be permitted to jump the queue ahead of legal applicants waiting patiently for visas back in their home countries. And Congress should add other conditions. Those already in the country illegally should be required to pay a penalty; they should have to wait just as long as other applicants for full legal status. While they're waiting, they should be required to fulfill a variety of additional obligations: hold a job, pay taxes, abide by the law, take English classes, and demonstrate their commitment to American values. Once they've met these terms, it might even make sense to require them to go home to pick up their visas.

The vetting alone is sure to be a huge job, and it will have to be done with the utmost care on the part of law enforcement. But the truth is there's no other realistic way to eliminate the vast illegal world these immigrants inhabit: no other way to clear the ground in order to build for the future with a realistic, legal system of the kind the president envisions. After all, we as a nation aren't going to deport 10 to 12 million foreigners. However much they dislike the idea of illegal immigration, the American people aren't likely to have the stomach for that. Nor would it ultimately be in our interest. Surely it makes more sense to retain these trained, already assimilating workers than it does to send them home and start over with people who know nothing of the United States or its ways.

DOES THIS MEAN it may be possible to bridge the gap between the president and his conservative critics? Well, yes and no. The critics are right about many things. Our current "nudge, nudge, wink, wink" policy is unacceptable. The erosion of the rule of law cannot continue. We must secure our borders against terrorists. The critics are also right to be worried about the costs that even legal immigrants impose on social services--primarily schools and hospitals--in the communities where they settle. Any overhaul of the immigration system must deal with those costs, and it ought to include a set of provisions, both carrots and sticks, to encourage assimilation. About all of that, there can be no doubt. The only catch: Just think a minute about this list of concerns. In fact, what the critics find intolerable is not the president's plan; it's the status quo.

The Bush package acknowledges the critics' concerns and attempts to address them with realistic solutions. It's designed to serve America's economic interest. It's our only hope of ending the hypocrisy that undermines our law enforcement. It's the best way to restore the rule of law in our workplaces and enhance security on the border. Issues of assimilation and local service costs are among the practical matters still to be thought through--on the table for Congress to tackle as it writes the legislation to implement the president's plan. But surely eliminating the barriers that now prevent 10 to 12 million U.S. residents from participating in the body politic and requiring them to pay their full freight in taxes would be a good start on both problems. And this can be accompanied by other, more proactive strategies like mandatory health savings accounts for guest workers and incentives for employers to offer them English classes.

Where the critics are most wrong--where they seem most shrewd but are ultimately the most misguided--is in their view of the politics of immigration. Here, too, they see the symptoms accurately enough. Americans are frustrated and angry. They know the system is broken; they want change. Uncertainty about just how to effect that change is driving a wedge into the Republican party, dividing the president from his conservative base in Congress and at the grassroots. And if the system isn't fixed, it could create a dangerous opening for Democrats: an opportunity for Democratic immigration hawks to outflank Republicans, not just on law and order, but even more devastatingly on security. All of this is true--and scary. But the answer isn't to block reform. The antidote is to deliver a remedy, as the White House proposes.

The president isn't misreading public opinion. If anything, he reads it better than his critics do. Most Americans aren't anti-immigrant. As poll after poll shows, what they want is to regain control--of both the border and the underground economy. The paradox at the heart of the Bush plan makes it a little hard to explain to voters. The president is promising to regain control by means of a more generous and welcoming approach to immigration. But that doesn't change the underlying truth: The Bush plan is the only way to restore the rule of law, either on the border or in our communities. It's the best answer to the critics' complaints, the only answer to the illegality that plagues us. And surely--no matter what the skeptics say--it can't be political suicide to give voters a solution to one of the problems that frightens and disturbs them most.

Tamar Jacoby is a senior fellow at the Manhattan Institute.