SUDDENLY AND SURPRISINGLY a black man, Jesse Jackson, finds himself labeled the early front-runner for the Democratic nomination. In a blink Jackson has gone from a 1984 minor-league candidacy centered on the novelty of a black running for president to a 1988 role as a leading contender for the big-league championship.

But as a black person who observed Jackson up close in 1984, I see danger lurking beneath the euphoria and racial pride surrounding Jackson's breakthrough -- danger for black voters, for black elected officials and for the Democratic Party's chance to win the White House. I believe black and white Democrats alike need to wake up to the danger now.

Three starks facts stand out:

Jackson cannot be elected president.

Rather than increasing black influence in the primaries and in the Democratic Party, a Jackson candidacy will nullify it by discouraging other candidates from seeking black support.

As long as Jackson remains in the spotlight, he prevents other black politicians who could appeal to a broad spectrum of voters from rising to power.

We ought to be clear about what Jackson's candidacy represents. Jackson is the last gasp of the black political leadership generated by the civil-rights movement. His roots are in a time when elected politics was closed to blacks. His 1984 candidacy was a crusade/protest movement made to fit into the format of the presidential campaign. For black America, still suffering from Ronald Reagan's callous racial policies, the 1984 Jackson campaign was a national revival meeeting. In debates he raised the issues of concern to black Americans. He challenged the corporations and even the sports leagues that have no blacks in management. He scolded the unions and the Democratic Party for taking black dollars and votes for granted and doing nothing to earn that support.

And Jackson was wonderful!

But that was then, and now we have to dispense with symbolism and think about ways to translate our numbers and position in the party into real strength.

The foremost danger in his candidacy now, to my mind, is that Jackson will be eliminating blacks as a factor in the Democratic presidential primaries. He will pull black voters and their voices in line behind him, but out of the way of the competition to define the future of the party and to pick its presidential candidate.

If black voters are uniformly lining up behind Jackson, then other Democratic contenders will not give priority to black voters. At best the candidates will compete for the few blacks not on the Jackson bandwagon so they can advertise themselves as having some black support; but black support will not be crucial to the success of their candidacy in this crucial campaign at the end of the Reagan era.

The irony of Jackson's candidacy is that it is segregating blacks into a second-class status in the Democratic Party. "The gravest result of Jackson's {1988} candidacy is that it reinforces the disposition of blacks not to think of themselves as full citizens in the polity," said Adolph L. Reed, Jr., associate professor of political science and Afro-American studies at Yale University and the author of "The Jesse Jackson Phenomenon," which analyzed Jackson's 1984 campaign. "We {blacks} don't have a proprietary relationship with the party and the candidates. We have a tendency to talk about the party and the candidates as 'them' not 'us.' But the fact is that black people are a key part of the party. We've been in the Democratic Party for 50 years and its future is amenable to our engineering if we have an agenda and can form coalitions with others in the party. Unfortunately, Jesse Jackson is pulling us away from the political process, the political debate."

Although black positions will obviously be well represented in the Jackson camp, no one will be able to speak with credibility and power for black interests in the councils of the other candidates. The absence of blacks as a factor in the 1988 primaries for candidates other than Jackson will magnify the influence on the rest of the field of the party's right-wing, neo-conservatives who have been pushing the party to ignore black concerns and mimic the Republicans since Jimmy Carter's defeat.

Even if blacks eventually come around to supporting the party nominee, it will be too late. The key to influencing a candidate is supporting him or her early. Latecomers get leftovers. By the time blacks again become a factor in the big tent of Democratic party politics -- in the general election when their turnout will be treasured by the Democratic nominee -- it will be too late to extract the pledges of support for social spending and affirmative action that are at the top of the black political agenda. It will also be too late to join in coalition with liberal white Democrats to assure that the party's nominee opposes further U.S. intervention in Nicaragua, is pledged to oppose apartheid in South Africa actively and is serious about a nuclear-arms agreement.

This dynamic will be in full flower in the southern regional primary. Jackson is expected to get about 90 percent support from blacks in the South. That leaves the remaining Democrats to compete for white, southern votes on a playing field defined by the neo-conservative, southern, white agenda. Jackson may even come in first in the southern primaries, but blacks will have excluded themselves from the intense fight to shape the party's self-image, its future and to pick its candidate.

Now we come to the second danger inherent in Jackson's 1988 campaign. It diverts black voters from the true goal of any presidential campaign -- winning control of the White House. Black voters have to realize that Jackson is not going to win the presidency. It's not even in our interest to have Jackson as the Democratic nominee if winning the White House is the point of the game -- and it is. Jackson can't bring home the big prize.

It's unfortunate but true that race remains a real factor in our national life. We have no black senators. Only one has been elected since Reconstruction. We have no black governors and only one lieutenant governor. Jesse Jackson is known to 95 percent of black voters and 90 percent of white voters. He has won more support than anyone expected, and it is evidence of his genius and persistence that he has overcome so much to become the most inspiring figure on the American political scene. He has overcome bitterness and racism in the Democratic Party and from the press, as well as jealousies from some black politicians, to achieve his high stature.

"There's no question that if he were white he'd be president," says Frank Watkins, Jackson's spokesman.

"There's a double standard set for Jackson," said Michael Lomax, chairman of the Fulton County (Ga.) Commission. "He's got to justify himself and his candidacy to voters in ways that other candidates do not have to because he is black."

"Race is a severe limit on Jackson," said Ron Walters, professor of political science at Howard University and a top advisor to Jackson. "When people say to me 'What does Jesse want?' I hear underneath that the question 'What is a black guy doing running for president?' and beneath that is the question 'Should a black man be president -- do I want to be represented by a black president?' This is very deep. People will not come out and say it but that is the case."

Indeed, race remains a central fact; so does Jackson's flashy rhetorical style, because it offends so many white voters. The biggest fact is this: Jackson continues to have very high negatives with voters. About 50 percent of Democrats have said in repeated polls that they will never vote for Jackson. After Gary Hart dropped out of the race Jackson actually lost support in Iowa.

Even the white farmers he has been wooing for years speak cynically when asked if they will vote for Jackson. Gordon Waller, a Montana farmer, was flown to Miami last month by Jackson's campaign to appear publicly in a show of black and white, urban and rural, together. But when a reporter took Waller aside and asked him if he planned to vote for Jackson, this man Jackson brought with him as evidence of his support in the farm community, replied: "I would rather not answer that right now."

What the farmer is saying that he's happy to be with Jackson because Jackson speaks eloquently of the crisis facing American farmers. If farmers were not with Jackson, their anger and resentment might well take them to a right-wing extremist like Lyndon LaRouche. Jackson can't expect white farmers, much less white suburbanites, to vote for him in sizable numbers.

Black Democrats should not buy the illusion of a Jackson-farmers alliance as justification for giving uncritical, uniform support to Jackson so he can focus on making deals with whites, such as the farmers, in the hope that they will support Jackson. That is a con game. And the people being conned out of their political power are black Americans who need to focus on putting a strong ally in the White House to repair the damage of the Reagan years.

Black America is not a monolithic political body. Not all black people have Jesse Jackson's political views. In fact, I covered Jackson, and other than saying that Jackson is sensitive to issues of concern to blacks, I still can't tell you what his policy positions are on most issues because he got around to spelling them out only at the campaign's end in a rush of printed position papers written by academics.

Jackson's appeal to the black community -- his rhetoric about a rainbow coalition notwithstanding -- is less about policy issues than it is about a black man running for president. All debates about social policy and foreign policy in the black community are subsumed in the rush to show racial support for a black man running for president.

For black America to do that again, in 1988, when the future of the party and the White House are on the line, is to say that racial pride is the only concern of black Americans. It is absurd to think that if Jackson makes a good showing in the primaries because of unified black support, then black America has done well for itself in 1988. That is the equivalent of saying that since Bill Cosby is doing okay, then black America is doing okay, although a third of black America lives in poverty.

This idea of one black man as the fulfillment of all black political aspirations has been breaking down steadily since 1984. In Gary, Ind., Richard Hatcher, who gained attention in 1967 as the nation's first black mayor and who headed Jackson's 1984 campaign, was recently defeated. In Newark, Kenneth Gibson was defeated last year after 16 years in office. Rep. Peter Rodino won re-election in New Jersey despite Jackson's intense campaign to get a black candidate to represent a mostly black congressional district. The voters chose to retain the senority and power Rodino possesses instead of accepting the self-indulgent token of a congressman who can do less for them -- but who has black skin.

This changing attitude is already affecting Jackson's own black support. Black middle-class voters overwhelmingly supported Jackson's crusade/protest candidacy in 1984. They gave him more support than poor blacks. But in this campaign a poll done by the Joint Center for Political Studies, the major black think tank and political study group, has found a 9 percent drop in Jackson's support among the black middle class, from 67 to 58 percent. The drop can be seen in the lack of support Jackson is getting from black Democratic leaders in the South, where most black Americans live, from Mayors Lottie Shackelford of Little Rock, Richard Arrington of Birmingham, Andrew Young of Atlanta and Harvey Gantt of Charlotte.

"I love Jesse Jackson -- but I'm sure he can't win," said Beulah Shepard of Houston, a 1984 Jackson supporter, in explaining to reporter Priscilla Painton of the Atlanta Constitution why she is not supporting Jackson in 1988. "I don't have time to waste with somebody who can't win. I don't want any more Republicans in the White House."

"We've gone through the days of protest and now it's time to make a contribution to the party," said Rep. John Lewis. "I spoke to a group of labor people from Georgia and other parts of the South {recently} and I got the sense from these folks that it's time to win. They really want to win the White House."

The third major danger of the second Jackson candidacy is that he is now crowding out younger black politicians who need some time in the sun to grow into major forces in the Democratic Party. In his last race Jackson won the title of pre-eminent spokesman for all black America. He often won primaries in cities with large black populations despite the opposition of local black leaders like Wilson Goode, Coleman Young and Tom Bradley. Jackson's 1984 crusade did not permanently damage these local black leaders. But it did weaken them, both locally and in the party, because they couldn't deliver votes -- the be-all and end-all in measurements of political strength. A second round of being run over by Jackson will further weaken this first generation of black American politicans.

Jackson's answer to this complaint has been that he has "coattails"; the excitement he generates among black voters benefits local black officials. But that boast simply isn't supported by the facts. On the contrary, black politicians he has supported have lost repeatedly. Ken Spaulding in North Carolina and Katie Hall in Indiana, both candidates supported by Jackson, actually lost on the same day that Jackson was running in 1984 primaries in their states. In fact, Spaulding and Hall drew more votes than Jackson. Did Jackson run on their coattails? In some cases local politicians actually run away from Jackson so as not to alienate white voters -- Douglas Wilder, the lieutenant governor of Virginia, asked Jackson not to campaign for him.

Next year Jackson is likely to get little direct opposition from local black officials. They know he can beat them on their own turf and they don't want to be positioned as opponents of the fabled Jesse Jackson. But resentment is building. Jackson is effectively choking these black politicians into compliance and thereby strangling their growth as power players in the Democratic party. Because black politicans around the country can't bring large numbers of black voters with them, few will win positions as key advisers to other top Democratic contenders.

Jackson is also stifling the ambitions of local black political leaders who dream of moving up in the party to the point of running for president themselves. There are several black Democrats who would do much, much better than Jackson with white voters. Mickey Leland, Andrew Young, Tom Bradley, William Gray, to name four politicians, are all capable of winning more delegates to the convention than Jackson. They operate comfortably within the political system; they don't have Jackson's high negatives; they have support from their white peers; and they have local political bases.

Jackson's protest politics become corrosive when they begin to put a ceiling on other black politicians who could be moving into the arena of national black politics. And that is what is happening now. Black politicians are afraid to go into the competition inside the party because if they come into conflict with Jackson they will be branded traitors to the race.

The loss of black political growth is the most damaging consequence of Jackson's second candidacy.

The point here is not that Jackson should not run a second time. It is that black voters and politicians need to operate as political free-agents in the upcoming primaries. As free-agents black Democrats can get the best political deals for themselves.

But what if Jesse Jackson does well in the primaries and the Democratic convention is deadlocked. Won't that give him -- and blacks -- leverage? As the various candidate wheel and deal at a brokered convention, they would be hungry for black support. And if that support were spread around, waiting to coalesce behind the best offer, candidates would be anxious to make deals.

But if getting black supports means caving in -- or appearing to cave in -- to a Jesse Jackson, who will strut and pronounce himself the kingmaker, then the price of black support may be too high for the competing candidates. No Democratic candidate will want to go into the general election carrying that stigma. On the other hand, any Democrat would love to go into the general election saying he has the support of black Democrats. That posture will enhance a candidates' chances in the general election by enabling him to say he is a man of all the people.

Black Democrats can have a role in shaping the party's future. They can ensure that the party's candidate is indebted to black voters. And they can help the Democrats win the White House. That is the real prize; at this point settling for the emotional release of another Jackson campaign amounts to settling for the booby prize.

Juan Williams, who covered Jesse Jackson's 1984 campaign for the Democratic nomination, is a Washington Post reporter.