US attorney's inquiry harries Mayor Barry. CORRUPTION PROBE IN US CAPITAL

Marion Barry, reelected last November to a third term as mayor of Washington, D.C., with 61 percent of the vote, has had to contend, for the past 20 months with both real and rumored corruption in the capital city's government. So far Mr. Barry, himself, is legally unscathed. But the cloud over City Hall has been, at the least, distracting. Yesterday a former top aide to Mayor Barry pleaded guilty to taking $1,500 from a special city fund to pay for a fur coat for the mayor's wife. The government has no evidence that Mayor Barry knew of or was involved in the illegal expenditure. The plea was part of an agreement with a special team of federal investigators who are probing alleged corruption in the city government.

Some details of an ostensibly undercover investigation by the Federal Bureau of Investigation and the office of United States attorney for the District of Columbia, Joseph E. diGenova, have been disclosed in recent months. A major probe into contracting practices of the district government was initiated, according to Mr. diGenova's office, after some ``civic-minded government contractors'' alleged there had been payoffs and fraud in connection with the awarding of city contracts.

``The investigation is proceeding on course,'' says Clendon Lee, spokesman for the US attorney. He won't confirm whether the mayor is a target.

Mayor Barry, who has not been called before the grand jury, says the investigation is ``narrow in scope.''

He ordered the District of Columbia Police Department's public integrity unit to conduct its own investigation. But the Washington police have not escaped FBI scrutiny. On Sept. 9, federal agents searched the vice office of the department's Fourth District looking for evidence that some officers took money and drugs confiscated from dealers. District of Columbia Police Chief Maurice T. Turner Jr. says the alleged wrongdoing is ``an isolated case'' involving only a few officers.

H.R. Crawford, councilman for Ward Seven, the second-poorest ward in the city, says the probe, which he thinks is racially motivated, has created a climate that hurts city business.

Some Barry critics say his record as mayor demeans his reputation as a civil rights ``foot soldier'' who helped blacks to participate in mainstream political life.

But Calvin Rolark, a grass-roots politician in Ward Eight, the city's poorest, and publisher of a weekly community newspaper, says he feels that US attorney diGenova ``should indict him [Barry] or leave him alone.''

The mayor's popularity remains high, especially among poor constituents. That popularity, according to Mr. Rolark and others, is justified by his works. Local businessmen and clergy have conducted rallies at the District's City Hall protesting the federal probe.

Barry is credited with reducing crime, revitalizing downtown Washington, constructing a new rapid transit system, and developing some 50,000 new private-sector jobs. ``The people who criticize the mayor are the people who haven't lived in the city long enough to know what services were before,'' says John White, Barry's press secretary.

``The city's got ups and downs,'' says City Council chairman David Clarke. ``But crediting the downs to corruption as opposed to inefficiency is a distinction I can't make.'' Problems with city ambulance service have caused ``tension'' between the council and the mayor for five years, says Mr. Clarke. ``You can't say a problem like that is a result of a probe.'' He adds: ``Public housing is a mess, and that predates the probe.''

Charges of corruption may be hampering the city's ability to recruit personnel, says Clarke, and this is a major reason why the US attorney should ``put up or shut up.''

Barry's income tax statements, bank accounts, and credit card receipts have been examined by federal agents. Press secretary White says ``boxes of documents'' have been routinely sent over to United States Attorney diGenova.

Meanwhile, rumors of philandering and drug involvement swirl around Mayor Barry. His association with Karen Johnson, a convicted cocaine dealer - with whom the mayor acknowledged having a ``personal,'' but not intimate, relationship in 1984 - has damaged his image. And Ms. Johnson has appeared before the federal grand jury twice in recent weeks.

The mayor flatly denies drug use and has urged the US attorney to come forward with substantiation of these allegations.

``The way the prosecution has proceeded has been highly unfair,'' says Barry's attorney, Herbert O. Reid Sr. ``Calling names and innuendo is not law enforcement.''

Mr. Reid says diGenova has leaked unsubstantiated charges to the media in hope of generating evidence. The primary result of the investigation so far, says Reid, has been to cast a pall over the city.

According to Reid, former deputy mayors Alphonse Hill, who pled guilty to defrauding the city of $300,000 in contracts, and Ivanhoe Donaldson, who was convicted of stealing $190,000 from the city, were prosecuted as a result of facts brought to light by the city's own inspector general.

Barry says the probe is a product of Washington, D.C., being under the thumb of the Congress and without an agency to conduct high-level investigations. ``This is another example of why we need home rule,'' he adds.

City services ``are generally okay,'' says Craig Baab, president of a citizens association in affluent, mostly white Ward Three. ``But what I'm not too crazy about is a racial divisiveness in the city. This is a segregated city.... The mayor should be bringing the city together. When you get charges of racism going both ways, that doesn't help.''