Vernon Jordan, the president of the Urban League, is one of the few people I have ever known -- John B. Connally is another -- who could go through an assassination attempt, be severly wounded and come away from the experience as clear in his judgement and unemotional in his tone as he was beforehand.

So when Vernon Jordan says on a national television program, as he did the other day on CBS' Face the Nation, that "there is an unusual amount of hysteria in the black community," it needs to be taken seriously.

There is no mystery about the source of that "hysteria." It has been fed by economic forces, instances of violence and fears of political reprisal. While inflation has been a curse for every American, the decline in real incomes has been felt with particular severity in communities where there are more poor and unemployed than anywhere else.

But black communities have also reacted with anger and fear to unsolved waves of murders in cities like Atlanta, and to the acquittal of whites involved in deaths of blacks in Greensboro, N.C., and Miami, among other places. Even the unsolved assault that hospitalized Jordan and nearly claimed his life earlier this year has added to the tension.

Last month's election was an added blow to confidence of black Americans about their prospects in this society. It is easy -- and, to some extent, accurate -- to say this fear resulted from the exaggerated rhetoric President Carter used in his efforts to rally black support to his side. But there is also a reality that blacks understand and that whites need to understand as well, in order to recognize the danger of social disintegration that men like Jordan foresee.

The political reality is this: blacks were transformed by the 1980 election from being at the very center of a coalition that brought a president to power to being the most conspicuous outsiders at the new government's victory celebration. It is only by understanding the extent of that power transformation that one can glimpse the reasons for the "hysteria" of which Jordan spoke.

Jimmy Carter was more indebted to black voters and black leaders than any other president in our history. It was the testimony of black leaders from Atlanta that first persuaded skeptical white liberals to support the lame duck governor of Georgia against George Wallace in the Florida primary of 1976. Their testimony rescued him from serious trouble in the "ethnic purity" escapade in the spring of 1976. Their votes provided the margin of victory for him in the crucial Florida and Pennsylvania primaries and in the general election of 1976.

When Carter acknowledged that debt by recognizing blacks with more appointments to positions of power in government than they had ever previously enjoyed, he was doing no more than politics and conscience dictated. Blacks -- including Jordan -- had their disagreements and disappointments with the economic policies of the Carter administration, and they voiced them vigorously.

But in the election last month, as Jordan remarked, just about "the only group of voters who stayed on the sinking ship were black voters." About 85 percent of the blacks supported Carter, a figure that was approached only by the Hispanics. Almost every white element of the old Democratic coalition saw serious defections to the Reagan-Republican column.

And that was not the end of it. Despite pre-election assurances from some prominent white liberals that the future of the courts would be "protected" from the consequences of a Reagan victory by the Democratic majority in the Senate, that safeguard too was swept away in the political revolution of Nov. 4.

Now, blacks know that it will be Sen. Strom Thurmond (R-S.C.), who bolted the Democratic Party to protest its commitment to civil rights, and not Sen, Edward Kennedy (D-Mass.), who will be conducting the hearings on Reagan's judicial nominees.

Thurmond has called already for repeal or substantial revision of the Voting Rights Act of 1965, perhaps the most effective step ever taken for the political empowerment of blacks. Other new Republican Senate committee chairmen are talking about curbing or outlawing affirmative action programs, curtailing food stamps and other programs whose benefits are of particular value to the victims of poverty and discrimination.

Under the circumstances, it requires no great sensitivity on the part of whites to understand the "hysteria" of blacks. Reagan himself, his transition budget supervisor, Caspar L. Weinberger, and such prominent Reagan supporters as Rep. Jack Kemp (R-N.Y.) have gone out of their way to assure blacks that they need have no fear of the consequences of the political shift.

Jordan, for one, says that he is prepared to give Reagan "the benefit of the doubt" and to defer judgment until he sees the appointments, the budget and the program of the new president. That deference is appropriate.

But in the meantime, all of us -- in our own communities and groups, our own jobs and associations -- ought to be mindful that this is a time when it is particularly important for communication across the racial lines that tragically still divide American society.