When Mitt Romney suggested “self-deportation” as a solution to illegal immigration at last night’s debate, his comments were met with confusion and a certain amount of derison. A few commentators pointed out that when the federal government gave 475,000 illegal immigrants a chance to turn themselves in and effectively self-deport, they were only three takers.

But Romney isn’t proposing a repeat of the ill-fated Schedule Departure program. Rather he is drawing on the attrition through enforcement strategy developed by think tanks like the Center for Immigration Studies and implemented by Arizona and other states (albeit over the objections of the Obama-led federal government). CIS executive director Mark Krikorian has described it as an approach to change incentives for illegal immigrants through verification and targeted enforcment:

Shrink the illegal population through consistent, across-the-board enforcement of the immigration law. By deterring the settlement of new illegals, by increasing deportations to the extent possible, and, most importantly, by increasing the number of illegals already here who give up and deport themselves, the United States can bring about an annual decrease in the illegal-alien population, rather than allowing it to continually increase. The point, in other words, is not merely to curtail illegal immigration, but rather to bring about a steady reduction in the total number of illegal immigrants who are living in the United States. The result would be a shrinking of the illegal population to a manageable nuisance, rather than today’s looming crisis.

The idea is that illegal immigrants are coming to the United States for jobs. Make the jobs harder to obtain illegally and not only will fewer come, but more will leave. The whole process can be done more gradually and more humanely than a mass deportations regime. Of course, it cannot be done totally painlessly or without any political opposition.