If Mayor Marion Barry and U.S. Attorney Joseph E. diGenova were prizefighters in a 10-round match, we'd be in the 50th round by now.

Gaining several points when his office struck that dizzying series of jabs against alleged corruption in District government contracting nearly two weeks ago, diGenova announced the end of the 17-month undercover phase of an investigation by making it startlingly public: He papered the town with 15 subpoenas and FBI agents conducted a spate of searches. The flurry rocked Barry's entire administration and kept the mayor on the ropes for several days.

When Barry recovered enough to respond in a news conference, he insisted that he was not the target of the long-term federal investigation. To some of us, weary from having heard Barry say the same thing during earlier federal probes into alleged corruption, that statement sounded a bit empty.

But now it's become increasingly uncertain whether diGenova's high-stakes game will actually reveal the organized, widespread conspiracy to defraud the government among current and former city officials and contractors that he set out to show. To date, no criminal charges have been filed and no indictments have been returned. And when asked directly whether Mayor Barry is a target of this probe, diGenova refuses to comment.

When residents first heard of diGenova's investigation, many felt furious that potentially widespread corruption existed at city hall, and encouraged the probe. Corporation Counsel Frederick D. Cooke Jr. was exactly right when he said the other day that D.C. employes were "all suspects." Cooke might have added that every contractor with the city is similarly under a cloud.

Now many residents are asking themselves whether diGenova actually has evidence that will prove his theory of widespread organized corruption, or is merely on a fishing expedition. I don't mean to flack for the mayor, but it's a good question. Although diGenova has assigned 10 of his most experienced prosecutors to pursue and analyze the FBI-collected evidence, even insiders don't seem to know the answer.

Three issues are of monumental importance here: the role of the mayor; the allegations that Karen K. Johnson, the convicted cocaine dealer and a former close friend of the mayor, was paid by city contractors not to testify on drug use by city officials; and allegations of broad-based corruption in the contracting program.

Given the deafening silence from diGenova on any aspect of the probe, some city residents are also beginning to question his motives. Indeed, if he is after Barry and has gone through 17 months of a "sting" operation, including wiretaps, and has only two pairs of Barry shoes to show for his subpoenas, either his motives or his skill at undercover work might reasonably be questioned. Because he has unsuccessfully sought to implicate Barry criminally in the past, some people wonder if this is just another vendetta against the embattled mayor.

Other residents object to the public way diGenova handled the subpoenas and searches. Some people "issued subpoenas could just have been called on the telephone and asked to bring whatever information the U.S. attorney was seeking down to his office," said one local lawyer. "They wouldn't have treated white businessmen that way."

Still others, suspecting political motivations on the part of the Republican U.S. attorney, worry that diGenova is trying to strike fear among the city's minority businessmen.

While I am willing to give diGenova the courtesy of believing he is simply doing his job in trying to root out graft and corruption, which obviously no one wants to tolerate in government, his actions have shocked and disturbed this community, arguably further polarizing it racially. Now, basic fairness dictates that this probe not be permitted to fester.

The time has come for diGenova either to put up or shut up, if for no other reason than to unlock the paralyzed city government. It's time for somebody to score a knockout in this fight.