"The black strategy should be to hang loose and make the candidates come to us. No one can win without the black vote."

Brave words, spoken by the most impressive of black leaders, Vernon Jordan, of the Urban League. But the 70th anniversary convention of the league here in New York belies that claim and expresses the pathos of black leadership.

All the presidential candidates, to be sure, showed up. All spoke with Jordan in the hospital, where he is still recuperating from the shooting that struck him own in Ft. Wayne, Ind., over two months ago. But, in one way or another, all came bearing warnings.

President Carter had to explain away a recession that is making blacks its chief victims. John Anderson charged that the nation had "declared a truce in the war on poverty." Sen. Kennedy warned against the "forces of Reaganism" and "negative reaction." Reagan, though he delivered a speech so fine in form and content that it touched him with the aura of statesmanship, claimed mainly that he wasn't as bad as many blacks feared. "Perceived barriers between my political beliefs and the aspirations of black Americans," he put it, "are false."

Theoretically, the convention should have been able to bear manfully the word that the fortunes of black Americans could not prudently be left to the play of politics and government. To an outsider, at least, the delegates to the Urban League convention presented the spitting image off confident, self-reliant Americans. They showed themselves responsive in meetings and serious in workshops. They managed the convention apparatus, with all the appalling complexity off candidates, Secret Service and press, in brilliant fashion.

But they did not want to acknowledge the black ascent to middle-class status nor the responsibility it implies. In a speech published in the program, Jordan, while admitting "progress in corporate jobs" and "in schools and colleges," attacked the concept of black progress as a "dangerous illusion."

Emmett Rice, a black member of the Federal Reserve Board, spoke out explicitly on behalf of "helping ourselves . . . taking our economic destiny into our own hands." But he said that "this is the kind of statement most of us -- myself included -- least like to hear."

Far more appealing to the convention was putting the monkey on the back of race prejudice and government failure. John Jacob, who is No. 2 to Jordan at the league, spoke of "raw racism" and a "volcano of deprivation." A special study demonstrated at great lengths that many eligible blacks were not receiving welfare or other federal benefits. It concluded with a call for more "effective targeting" of "government programs to the black community." It insisted that "full employment be made a No.1 government priority."

The pathos of black leadership begins right there. By force of habit and the pressure of professionals, black leaders are driven to call for more and more government help. But however poignant, the appeals for assistance do not now find a positive response in the white community. There is no majority for more government help for poor blacks.

White leaders, on the contrary, can expand their political influence by standing up against such help. Edward E. Koch, the mayor of this city, for example, regularly goes out of his way to oppose affirmative action on behalf of blacks in schools and the professions. Polls show he has no following among blacks.

But he has widened his political base from Greenwich Village to include midtown Manhattan, the Bronx and Queens. He probably will be reelected next year with the backing of both Democrats and Republicans. He has become a truly popular mayor -- and a living disproof of the contention that "no one can win without the black vote."

Black leaders, conversely, have been thrust into losing confrontations. Far from being able to hang loose, they see themselves steadily reduced in stature by the experience of asking and not getting. Their inability to deliver the goods is particularly perceived in the inner city, where, as in the case of Miami, young blacks run out of control.

That explains why Vernon Jordan is perhaps the only black left with a truly national following. That explains why so many black leaders have been losing influence. Through the workings of vicious circle, it happens that the unwillingness of middle-class blacks to shoulder responsibilities commensurate with their gains causes leaders to lose followers and race tensions to rise in a way that has to haunt all Americans.