Andrew Jackson Young, former U.N. ambassador, two-term congressman and civil rights veteran now come home to run for mayor, is one of eight candidates in a race in which the most explosive issue -- the city's missing and murdered black children -- is almost never discussed.

"The alternative [talking about it] would be to put the police and the city on trial," Young said today. "Our objective is to put the killer or killers on trial. No one can profit by second-guessing and drugstore quarterbacking."

With 23 black children and youths killed, another believed kidnaped, and the body of yet another discovered this afternoon, local police say they are no closer now to an arrest than nearly two years ago, when the murders began.

And some middle-class black leaders worry that because all the murder victims come from improverished neighborhoods the winning ticket has counted on for support in the past, the issue of the unsolved killings could turn poor blacks against those in power, or anyone associated with them, and make the race a free-for-all. Anyone, even a minority white candidate, might win.

Two weeks ago, the murdered children came up at an NAACP forum where 50 black residents from DeKalb County, where some of dead children have been found, turned out to grill police chief George Napper, a Ph.D. criminologist with little beat experience whom some of his men refer to as mayor Maynard Jackson's "ivory tower cop."

"If the number of dead children reaches 50 or 75, will you consider resigning?" asked NAACP lawyer Dwight Thomas. Two more bodies had just been retrieved from the Chattahoochee River.

"That question is too horrible to contemplate," snap Napper. He declined to answer.

Yet it's the kind of question citizens and officials are beginning to ask: At what point will Mayor Jackson, to save his political reputation and his power to help annoint his successor, consider cutting loose the men running the investigation? Never, vows Jackson, who has endorsed Young.

"Just watch," predicted Thomas. "In his final days, Jackson [legally barred from running for a third term] will be struggling harder than Jimmy Carter trying to get the hostages out of Iran. They've got to make some kind of arrest; otherwise, heads are liable to roll. And if the cases aren't solved and the cnadidates are able to make Young defend Jackson, anyone who enjoys the label as heir to Maynard has had it."

Young's principal black rival is A. Reginal Eaves, Jackson's former public safety commissioner who resigned under fire after a police promotion exam cheating scandal, but appears to enjoy support among many poor and some middle-class blacks. Other middle-class blacks are beginning to line up behind Sidney Marcus, a white state legislator and liberal respected by both blacks and whites.

Longshots in the race included a CIA agent turned lawyer; a white real estate developer named Henry Jackson who says he's deliberately kept his face out of ads hoping voters will think he's black; a socialist; a woman state representative, and a white businessman who announced his last campaign for city council in a Peachtree Street singles bar.

Should the black vote in the Oct. 6 election be so divided as to deny any candidate the absolute majority needed for victory, the stage could be set for a black-white showdown in the runoff.

Young scoffs at this scenario. "I don't feel [the child killings] will split the black community, but some hope that it will."

Two-thirds of the city's 480,000 residents are black, along with the mayor, public safety commissioner, police chief and chamber of commerce president. More than one out of 10 black families, however, has an income below the poverty line, alongside a thriving middle class.

But tension over the cases has unusually strained the traditional ties that bind, particularly between blacks who have "made it" and blacks who have not.

Perhaps the principal proponent for this point of view is Camille Bell, a middle-class woman who had fallen on hard times and lived in a downtown housing project when her child became one of the murder victims.

She blames middle-class black elected officials and police "insensivity" toward the poor for the months-long delay in launching the vestigation. She says many poor blacks feel more would have been done sooner had the children been white -- or come from middle-class or upper-crust black families.

Officials deny the charge, but, by Bell's account, the perception lingers in the projects. Such a perception, some black leaders fear, could lead certain cnadidates to exploit the chemistry of frustration will surely become more volatile if the summer wears on without an arrest.

Eaves is the only candidate to take a direct shot at the children's investigation. He has suggested the killer or killers would be behind bars if he were on the case.

Pushed for some comment on the probe, Young would only go so far as to say he'd take a "serious look" at the cases -- and the police brass he would inherit if he were elected mayor -- but only if the cases remain unsolved after his inauguration in 1982.

"The pressure on the Jackson administration to solve the cases is tremendous," says the Rev. Joseph L. Lowery, president of the Southern Christian Leadership Conference. "It comes from a black community that demands excellence and from a white world that is suspicious of the administration's competency to begin with. Blacks shouldn't have to prove their competency [by solving the cases], but the pressure is still there. The eyes of the world are on Atlanta and it's police force."

Last week's statement by FBI Director William Webster in Washington that four of the Atlanta cases had been "substantially solved" -- with no hint of any move by Atlanta police to make arrests -- did little to bloster the police's image. However, the Atlanta police were somewhat vindicated when the FBI failed to provide any new information that could produce arrests.

While the community still appears to stand largely behind Public Safety Commissioner Lee Brown, the pressure weights especially heavy on a city that spawned the cream of the nation's black leadership. Martin Luther King Jr., Andy Young, Vernon Jordan all got their start here. Coretta Scott King, window of the slain civil rights leader, Ralph Abernathy, Julian Bond and others still move and shake beneath a futuristic skyline of steel and glass in a city "too busy to hate," the saying goes, a city that has never had a race riot.

But what disturbs some black leaders in the potential resentment from the poor towards the middle-class, a sentiment Camille Bell has come to symbolize for some. At a party after the Sammy Davis Jr.-Frank Sinatra benefit here to raise money for the special task force investigating the cases, Bell, in an orange polyester evening gown, nursed a ginger ale and smarted at the swirl of well-heeled blacks in tuxedos and expensive furs.

"They aren't as far from the projects as they think" she said. "When [President] Reagan cuts the social programs and their jobs, they'll be moving back to my neighborhood. It's going to be fun to see them on the way down."

Some black leaders call such resentment understandable, even valid. "We're not blameless, just helpless," says Charles King, director of the Urban Crisis Center. "Blacks put their hope in electing blacks, but that's not the answer. Black politicians can't deliver either. Ironically, though, their election lets middle-class blacks off the hook. We can say, 'Let the mayor and the city council handle it.' But middle-class blacks could work harder to pressure forces that produce change. We should do more, as should whites."

Some say the emotional outpouring of concern by blacks across the country, the marches, the green ribbons, the money dispatched to Atlanta, represent on some Freudian level an expiation of guilt over not doing, or knowing what do do for poor blacks in their own back yards.

Indeed, to many in Atlanta, it often appears that the whirlwind is experienced more intensely outside the eye of the storm -- that the little drumbeating here may be misinterpreted as not caring for its own. "Some parents of murdered children have interpreted silence [by some Atlanta black leaders] as lack of concern," says John Lewis, a Carter administration action appointee turned banker and onetime director of the Voter Education Project. "But the concern is deep. People just don't know how to express it."

Lewis says that gains from the civil rights movement have shifted concern away from the black underclass, whose murdered children have refocused attention on their plight.

"In the days of segregation, we were all in the same boat," he said over a salad in a downtown restaurant that would have barred him 20 years ago. "Whether you were a black millionaire or a maid, you still couldn't stay in the Holiday Inn. But blacks have moved up and now the middle class and those with means can escape and live in another world, while poor blacks remain trapped in a world of poverty and despair."