The first surprise is to see the three men making common cause. Charles Ogletree, the suave Harvard law professor; Ed Koch, the often contentious former mayor of New York; and the Rev. Al Sharpton, the civil rights gadfly whose arrest Koch once ordered.

The second surprise is that, at a time when big-city politicians are exulting over the reduction in crime during the past few years, these men should be backing a proposal to reduce the effects of one anti-crime measure.

The biggest surprise, though, is the modesty of their proposal, which they have dubbed Second Chance.

The idea is simple. Nonviolent drug offenders who have completed their sentences would be eligible to enroll in a program of drug treatment, education and job training, which, if they complete it and stay trouble-free for five years, would make them eligible to have their criminal records sealed. A second chance.

It is their response to a hideous problem. In many American cities, roughly half of the young black men are in jail, on parole or probation, awaiting trial or being sought on an arrest warrant. Ogletree says the District of Columbia's chief judge, Eugene Hamilton, told them some 80 percent of black males between 14 and 25 are "in the judicial system."

The big culprit, as everyone now knows, is crack cocaine--or at any rate, the mandatory sentences that apply to possession and sale of crack cocaine. It takes only five grams of crack (compared with 500 grams of cocaine in the powdered form preferred by white abusers) to trigger a five-year mandatory.

Whatever the initial intent of that disparate penalty, the result has been devastating. Thousands of young men are in prison for needlessly long sentences. Their records make many of them virtually unemployable after they've served their time. And because they can't find decent work, many become more or less full-time criminals.

Second Chance, if enacted by the federal government or by individual states, would, its promoters say, give these despairing ones reason to hope and therefore reason to keep out of future trouble while working to get their lives together.

But if the pressures are as great as the advocates say, isn't five years after completion of sentence a long time for an ex-offender to stay clean in hope of having his record sealed? If the unsealed record is a barrier to employment, what's he supposed to do in the meantime? The main benefit of sealing the record is that it permits a job applicant to answer "no" to the question: Have you ever been arrested and convicted of a crime? If he can stay gainfully employed and crime-free for five years, then the added benefit of sealing the record seems fairly small.

Sharpton, Koch and Ogletree have thought of all these things, they said at a meeting with The Post's editorial board last week. What they hope is that employers will consider the fact that an applicant is enrolled in Second Chance and not wait the full five years before taking a chance on him. Their admittedly conservative proposal is designed to make it enactable. They say some state and federal legislators wouldn't countenance a record-sealing after only a year or two--and would not agree to expungement under any circumstance. For the same reason, the men limit eligibility to nonviolent, nonrepeat offenders who have not been convicted of sex crimes.

If it seems a long and modest solution to the problem created by mandatory crack sentencing, there may be good reason for caution. To start with, it's extremely tough to get legislators to step forward on behalf of reduced penalties for any sort of street crime. No one wants to be labeled soft on crime.

Indeed, the day the unlikely Second Chance trio called at The Post, the Senate adopted an amendment to a bankruptcy bill that would fix the crack-powder disparity by dramatically increasing the penalties for sale of powder cocaine.

The most likely result would be to increase the number of whites, Hispanics and blacks in prison, says Marc Maurer, a spokesman for the Washington-based Sentencing Project. "While 31 percent of powder cocaine defendants [in 1998] were black, the majority of the remaining 69 percent were ethnically Hispanic," according to Maurer.

It's hard to see who could oppose the modest measure. Anything that promises to draw significant numbers of young people away from a life of crime is worth trying.

Still, I can't avoid wishing that someone in Congress would show the courage to reconsider the mandatory sentencing legislation that produced this monster of unintended consequences in the first place. Congress needs to give itself a Second Chance.