It’s coming down to the wire on real immigration reform in the Senate, and as the pressure to reach some sort of compromise increases, senators will need to be careful to prevent their desire to pass a bill from leading them to pass the wrong bill. One test will be the question of arbitrary cut-offs to limit the scope of earned legalization. Under the proposal that emerged from the Senate judiciary committee, illegal immigrants who arrived before December 2004 would have been eligible to come out of the shadows, pay a fine and back taxes, and then apply for a temporary worker permit as the first step toward citizenship.

Such a provision would provide for regularizing the vast majority of the 12 million illegal immigrants already in the country, but setting a cut-off date around the period when, with President Bush’s re-election, it became clear that immigration reform was a possibility, would have avoided rewarding those who tried to short-cut the system by coming in expectation of an “amnesty.” Almost any cut-off date before then, however, becomes arbitrary. Some have proposed making earned legalization available only to those who have been in the country for five years or longer. If lawmakers buy that, they’ll be voting for a reform that won’t reform anything.

If one accepts that earned legalization is the best – nay, the only – way to deal with the 12 million illegal immigrants who are already here, it makes no sense to offer that option only to some. Otherwise, “reform” will succeed merely in perpetuating an underclass of undocumented residents, albeit of smaller scale. Nor is it logical for the senators to try to prevent guest workers, whether newly arrived or newly regularized, from getting on track for citizenship, although some are proposing that as another “compromise.” Temporary visas are likely to meet the needs of many immigrants who want to come to America to work for several years before returning to their home countries with the skills they’ve acquired and the money they’ve been able to save up while here.

But if history is any guide, many will want to stay, and without providing an opportunity for eventual citizenship, a reform bill would just create a permanent second class. This has not worked in countries that have tried it – Germany is an example – and there’s no reason to think it would work here. President Bush understands all this, as do the fathers of the current bill, Senators McCain and Kennedy. A filibuster-proof majority, however, doesn’t yet appear to have gotten the message. It’s hard to overstate how important it is that they catch on, and quickly. The immigration problem will only get worse as time goes on.

Leadership from the Senate will be vital for getting the House to go along. Comprehensive immigration reform is a much tougher sell in the House, so the Senate needs to pass a real bill right off the bat to make a House fight worthwhile. The next day or two are critical. The Senate can heed the call of the president and two of its most prominent members and pass a comprehensive immigration bill that would mark a real “reform.” Lawmakers can decline to act at all, wasting the effort they have put in and delaying the day of reckoning on immigration. Or, even worse, they could pass a cosmetic bill that not only perpetuates old problems but creates some new ones, too. It’s too late for them to turn back now, so their best bet is to charge full-steam ahead.