MAYOR MARION Barry and the U.S. Attorney's Office here have been in an adversarial relationship for years, and the conflict is now at its most intense. The mayor, after an FBI sting, is in 1835623469to seize on the acquittals of former D.C. Human Services administrator David Rivers and local businessman John Clyburn, both friends of his, who had been charged with conspiracy and bribery in connection with city contracts.

The mayor, making his by-now familiar and distracting use of the race issue, said after the Clyburn verdict Monday that the U.S. Attorney's Office "has waged a long and underhanded campaign to discredit the minority business community in Washington" and that it has "failed. The jury showed that Washingtonians are too sophisticated to be fooled by the thinly veiled attempts of the U.S. government to gut the Barry administration's successful partnership with the minority business community." After the Rivers verdict a few days earlier, he had issued a similar statement.

But that isn't what these cases stand for. There is always a temptation when a prosecution fails to say the case should not have been brought. The second-guessing instinct is the stronger when, as here, the investigation that led up to the prosecution has been so lengthy, semi-public and, by virtue of the put-up-or-shut-up debate it has inspired, semi-political. But here hindsight misses the mark.

Mr. Rivers and Mr. Clyburn both claimed the vindication that they are entitled to, though both were also notably more restrained in their comments than was the mayor. Mr. Rivers said during the trial that his main interest in the contracts in question was in fostering minority business; Mr. Clyburn said he was "networking" in the manner of government (and private) contractors the world over. There was no evidence that Mr. Rivers had received any payments. The government, despite a 17-month investigation and four-month trial, failed to prove its case against the two men.

Still, the U.S. attorney's office has gone after other officials in the Barry administration. Several, including some of high rank, have been sent to prison by the same criminal justice system and the same city jury pool that this time around produced acquittals. No prosecutor wants to fail; the office plainly thought it had another good case.

Any prosecutor walks a fine line between the contradictory mandates to be zealous but not to accuse falsely or lightly. Our sense is that the Rivers-Clyburn case was not an instance where the system failed but one where, all sides having done their jobs, it succeeded.