WATCHING THE relentless investigations of Washington's mayor Marion Barry and other prominent black politicians, many blacks have asked whether the Reagan Justice Department has unfairly targeted black officials for prosecution.

The answer depends on how you read the numbers.

A look at the raw data shows that black officials are, in fact, being prosecuted far more heavily than their representation in the population of elected officials. Among 465 public corruption probes over the last five years -- limited to high-ranking politicians above the level of school board -- 14 percent were targeted on black officials. But blacks make up only 3 percent of the nation's elected officials. Does this mean that prosecutors are racist?

Many of the black officials -- including recently convicted former Maryland state Sen. Clarence M. Mitchell III, Congressional Black Caucus chairman Mervyn Dymally, Florida U.S. District Judge Alcee Hastings and indicted Tennessee Rep. Harold Ford (D) -- say this is exactly what it means.

The prosecutors naturally disagree. Public corruption occurs and is rooted out, they insist, regardless of the race of the accused.

But the emotional, sometimes shrieking debate about whether blacks are harassed has continued for decades, precisely because neither the accused nor their accusers can prove their side is right.

Former New York Rep. Adam Clayton Powell Jr. crystallized the argument 20 years ago when he said that he had been stripped of his 22 years of Senate seniority and banned from the House simply for "acting like a white man." Powell was, in fact, convicted of documented misuse of public funds, but his punishment remains the harshest ever accorded a House member.

Democratic presidential candidate Jesse Jackson updated the argument and drew cheers from thousands of NAACP convention delegates last year by saying that unsupported accusations and indictments directed at black elected officials are "spreading like a political AIDS across the country."

In search of hard evidence on this troubling issue, I have conducted dozens of interviews and read through hundreds of pages of Justice Department Integrity Section documents over the last six months. This is my conclusion. Race can be a factor -- but not always because of racism.

The most obvious reason that blacks have become more frequent targets for investigation and prosecution is that their numbers in public office have increased sharply -- from 1,469 in 1970 to 6,681 in 1987. Winning elections has made black officials visible -- and vulnerable they say -- in a way that has not occurred since post-Civil War Reconstruction. Then, a growing base of black political power was curtailed through poll taxes and the legally-sanctioned segregation that followed the Supreme Court's Plessy v. Ferguson decision.

But even if indictments of black officeholders have increased more rapidly than their numbers -- and I could find no reliable studies on this point -- other factors besides racism have to be taken into account. One is that blacks have also been more successful in attaining higher office, this increasing both the opportunities for abuse and the chances that such abuse will be detected. Another factor is the Justice Department's aggressive post-Watergate pursuit of public corruption cases, especially on the state and local levels where black officeholders are most numerous. A final factor may be that blacks tend disproportionately to hold office in cities where corruption has traditionally been most common among all races and ethnic groups.

Still many experts feel that racism remains a part of the explanation. "There have always been prosecutors with particular mindsets who for whatever reason -- and racial prejudice undoubtedly plays a role -- chase after minority politicians who have made it," said Bancroft Littlefield Jr., a former assistant U.S. attorney in New York who was chief counsel to Massachusetts' anti-corruption commission and teaches at Harvard Law School. "I've seen that for 15 years in one way or another."

And Alvin Thornton, a politically-active Howard University political science professor, asks: when did the well-documented harassment that plagued such black leaders as King, Malcolm X, and Marcus Garvey stop? "Those of us who are philosophical about this would say that some of the issues that might prompt review of a black official might prompt a friendly phone call to a white public official," said Thornton.

Some political scientists, such as Peter K. Eisinger of the University of Wisconsin, also argue that if blacks are victims, theirs is the same problem that Boston's Irish suffered when they wrested control of city government from the ruling Brahmins at the turn of the century. The powerful do not cede their control over the political process easily. Mary Sawyer, an Iowa State University researcher argues that blacks are likely targets because they are less likely to represent mainstream constituencies. Said Sawyer. "The motive . . . is not just that the individuals targeted are black (but that) so many black officials practice progressive politics."

Hanes Walton, a Savannah State University professor who has written several books on blacks and politics sums up the situation. "Some of (the racially-motivated harassment) is very real and very carefully orchestrated. Some of it grows directly out of racism and a desire to keep black political leaders at a certain level of participation. Other efforts are purely political and based purely on the ambition of local people. Some of it is based on improprieties of elected officials themselves. People have not sorted it all out."

But many black politicians who have been touched, either directly or indirectly, by scandal don't think there is any sorting out to be done. They see a racist conspiracy behind their troubles. In Washington, for example, 12 members of Mayor Marion Barry's administration have fallen under the the scrutiny of federal prosecutors. In a brief filed on Barry's behalf last year, five black organizations and the National Black Leadership Council charged that such investigations are part of a "national policy to neutralize black political strength." Barry himself once likened the continuing investigations to "a lynching."

Those words were echoed in Baltimore Feb. 3 when Clarence Mitchell III was convicted for the second time in a month, this time on obstruction of justice charges arising out of his dealings with a Baltimore drug dealer. "They killed Martin Luther King," said Mitchell, a 24-year state House veteran known for his stemwinding oratory but indifferent job performance while in office. "They are just lynching me legally."

Supporters of Clarence Mitchell III have recently held church fundraisers in Washington and Baltimore to raise money for a legal defense fund for black officials. These "freedom rallies" have attracted such notables as former Rep. Shirley Chisholm (D-NY) and former Pennsylvania Secretary of State C. Delores Tucker. At an hours-long Congressional Black Caucus session on black harassment held last year, the mostly black crowd cheered black officials who recounted their versions of harassment and jeered the lone Justice Department official who offered the customary denial.

Mayor Barry, however -- on the advice of aides who see a potential political backlash among those who discount the harassment theory entirely -- has pointedly avoided such gatherings and even declined invitations to talk about the issue as part of a discussion panel. Moreover, I found that almost no one who has thought seriously about the issue subscribes to the conspiracy theory.

Charles H. King, the black president of the Urban Crisis Center in Atlanta sees the popularity of the conspiracy idea as a form of paranoia. "That's one of the psychological damages inflicted on us. We are never sure why things happen to us," he said. Milton D. Morris, the director of research for the Joint Center for Political Studies, a respected black think tank, suggested that conspiracy theories catch on because there are so few black officials "that when three get hit by questions and allegations, it looks like all hell is breaking loose."

Accusations of racially-motivated prosecutions have continued to dog the Justice Department, especially during the Reagan years. To each new charge the FBI or Justice has issued a carefully-worded and cool denial. "The overriding rule here for prosecutors is, you've got to go where the facts and the evidence take you," said William Weld, the current criminal division chief. "You can't be waved off whole areas of an inquiry because you're afraid somebody might criticize you."

Federal prosecutors often cite in their defense the massive public corruption cases underway in cities such as New York, Chicago and Syracuse involving white officials. For every black official prosecuted, they argue, there are 9 or 10 whites.

"Race and religion and ethnic classification haven't the foggiest thing to do with how you are going to investigate corruption or organized crime or a drug ring," said Rudolph W. Giuliani, who has gained notoriety as U.S. Attorney for the southern district of New York for high-profile corruption probes. Giuliani said that he has frequently been accused of bias even though his prosecutions have targeted few blacks. "When I began prosecuting cases against the Mafia, there were any number of people who claimed that I was persecuting Italians, which was ridiculous," said Giuliani, who is an Italian-American.

But despite these denials, despite the fact that thousands of white office holders are also prosecuted, despite the convictions of some of these prominent blacks, an important segment of the black community clearly believes the worst about the American system of justice. A Washington Post poll conducted late last year, for example, found 28 percent of those polled saying that most of the probes are "attempts by whites to discredit or embarass black leaders." Most strikingly, better educated and more prosperous blacks were more rather than less likely to subscribe to the conspiracy theory: Forty-one percent of blacks respondents who earn between $30,000 and $50,000 felt that way, as opposed to only 12 percent of black respondents who earned $12,000 or less.

Significantly, however, 50 percent of the blacks surveyed told pollsters they had no opinion on whether investigations are an attempt to discredit blacks and 12 percent agreed that probes were based on "real evidence." And, increasingly, new voices on the national political scene are suggesting that crying racism too often is akin to crying wolf.

Virgina Gov. L. Douglas Wilder and civil rights movement veteran Rep. John Lewis (D-Ga.), for example, feel that if there is a double standard, black officials should simply rise to meet and exceed the expectation. Wilder, the South's highest-ranking black elected state official, said in a widely publicized July speech that race is not a factor in investigations but that "a public official is a public official." In a more recent interview, he went on to say that harassment may exist, but that a black official must be big enough to take it. Moreover, he said, the public is usually smart enough to recognize witch hunts.

Georgia's Lewis, who cut his teeth as a leader of the Student Non-Violent Coordinating Committee and the Voter Education Project, shares Wilder's opinion. He won his Congressional seat after waging a heated campaign in which he challenged opponent Julian Bond to take a drug test. "Black elected officials cannot go around saying 'The others did it; we can do it and get away with it,'" said Lewis. "We cannot shield ourselves from our wrongdoing by the color of our skin. We must be judged by the same standards."

Many black leaders acknowledge their frustration that there is no way of proving allegations of racism in prosecutions. "So much of what we're dealing with in this arena is like a puff of smoke," said A. Jay Cooper, Jr., who founded the National Conference of Black Mayors while mayor of Pritchard, Ala. and was himself the subject of a federal investigation, later dropped. "You can't get your hands on it." It is a no-win situation, those who keep the debate alive say.

"If a person is told a white congressman has a house in the District and one in the suburbs, has kids in private schools and drives a fancy car . . . people say 'That's the way it's supposed to be,'" said Abbe Lowell. "If a black congressman has the same thing, people ask where he got the money."

In some quarters, however, the charge of racism is becoming less automatic and enthusiastic than it used to be. Even though well-known politicians such as Chisholm maintained at the emotional Congressional Black Caucus session on the subject last fall that bias in investigations is alive and well, many more officials hang back from the dispute, counseling caution.

"I agree it's impossible to ignore racism as a factor when you have overwhelmingly white prosecutors dogging black politicians," said the Joint Center's Morris. "But pull back and ask yourself some different questions. Should federal prosecutors lay off investigating the Barry administration because it might look racist? (Former Michigan Rep.) Charles Diggs was investigated, indicted and jailed and claimed racism all the way. Should they have said, 'Hey he's black; you can't do that?"

Oscar Eason, the president of Blacks in Government, a national professional organization, said that he believes harassment exists but that black politicians are going to have to learn to "play the game or be as pure as Caesar's wife and avoid even the appearance of sin."

"That's the price we have to pay," said the Urban Crisis Center's King. "White folks are in a fishbowl; they get to swim. Black folks are in a test tube; they have to go straight up and down." Gwen Ifill is a Washington Post staff writer.