Bank of America has inadvertently wandered into what might become the most interesting public policy debate of the next election cycle: illegal immigration. A week ago, the bank—the largest financial-services company in the country—began a pilot program to market its credit cards to people without asking for their Social Security numbers or other proof of citizenship. Without saying so outright, this seemed clearly a plan to turn undocumented, illegal aliens into Bank of America clients.

In a lawyerly way, Kenneth Lewis, Bank of America’s CEO, defends the policy in today’s Wall Street Journal. But the issue cuts much deeper than the policies of financial services companies. It really addresses the question of what we do with the millions of immigrants who have arrived here illegally and , in some cases, have been here for a generation or more.

No one in the political sphere has taken on this issue directly. Border security and guest-worker programs don’t address the real issue of how to deal with people who, other than their undocumented status, are productive and law-abiding citizens. Tracking down all of them and deporting them is wildly unrealistic. Yet perhaps the Bank of America credit-card approach is the first in what will be a series of steps to mainstream this population.

There will be howls of protest, especially from the more nativist elements in the Republican and Democratic parties. There will also be all sorts of national-security arguments, as there were when Tennessee tried to give drivers’ licenses to undocumented aliens. But there is no escaping the question of how to bring aliens into the normal channels of American life. Bank of America’s decision to stick to its policy suggests that this question might ultimately be determined by gutsy and entrepreneurial businesses, not by poll-watching politicians.