A decade-old legal drive by blacks to open up all-white city councils, commissions and school boards across the South may have been derailed Tuesday by a one-time benefactor -- the U.S. Supreme Court.

The court's ruling in a Mobile, Ala., voting rights case has immediately jeopardized black efforts to restructure governments in at least eight jurisdictions in Alabama, Mississippi, Florida and Louisiana, and has put hundreds of other potential cases in doubt, civil rights lawyers said yesterday.

White city officials, meanwhile, who say they have waited a generation for a favorable omen from the justices, said they now believe they have one.

"It's a message to the federal courts here that they've been meddling in local affairs too long and too much," said Lambert Mims, a Mobile commissioner.

"It has restored our faith in the American system."

Mobile is 35 percent black. Largely because it had never elected a black city official with its at-large election system, U.S. District Court Judge Virgil Pittman in 1976 ordered it to convert to a ward election plan.

A divided Supreme Court Tuesday overturned Pittman's order. It was not enough that blacks was never elected, the justices ruled. Blacks, in order to prevail, must show that the system of government was specifically designed to exclude blacks.

That requirement -- proof of intent -- did the damage, lawyers said yesterday. "The decision will make it very difficult if not impossible to make a case," said Frank Parker, of the Lawyers Committee for Civil Rights, who is handling cases similar to Mobile's in Jackson, Greenwood and Hattiesburg, Miss. "It is a serious setback."

"We may be out of business in some states," agreed James Blacksher, who filed the Mobile suit. "If the '60s was the era of the second reconstruction, we may now be in the era of the second redemption," he said, referring to a term some white southerners use to describe their return to power following post-Civil War Reconstruction.

"It may immunize" commumities from such suits, suggested Bruce Fein, a Supreme Court analyst in the American Enterprise Institute.

Black and civil rights observers regard the election of numbers of blacks to public office as among the most singnificant gains of the past 20 years. Once in power, they believe, the allocation of services, the administration of justice, education and the vote can be made fairer without resort to the courts.

Most at-large systems require all the voters in a jurisdiction to elect an entire council or commission without regard to ward or district. The voting majority thus can control the entire governing body. A minority, which might otherwise be able to seat one or two of its own from minority wards, may not elect anyone.

That was the pattern in Mobile, as in thousands of Southern and some Northern cities and counties.

With equal certainty, communities changing to a ward system -- Dallas, Montgomery, ala., Yazoo City, Miss., for example -- have elected blacks and other minorities almost immediately.

Those victories were facilitated by a 1973 ruling of the 5th U.S. Circuit Court of Appeals in the case of Zimmer vs. McKeithen.

The court, based in New Orleans, said that to win these suits under the 15th amendment's voting rights protections, blacks need not prove obvious discriminatory purpose in the design of at-large systems. It was sufficient to show, among other things, that blacks were excluded, that white government was unresponsive to blacks, and that there was a history of discrimination. These elements of proof became known as the Zimmer factors.

Civil rights lawyers say the Zimmer factors were critical in their victories. Purposeful discrimination, they say, was nearly impossible to prove in the Deep South because, when at-large systems were enacted around the turn of the century, white officials had no need to dream up an exclusionary structure of government. Blacks were already denied the vote in many places.

"They didn't have to worry about trying to finesse the situation with . . . at-large system," plaintiff Blacksher said. "They just kicked them out and didn't let them vote."

The Supreme Court decision Tuesday obliterated the zimmer criteria. Those criteria were "quite evidently decided upon the misunderstanding that it is not always necessary to show a discriminatory purpose," Justice Potter Stewart wrote for the four justices who controlled the opinion.

Many rights lawyers held out hope that, because it was decided by a four-man plurality (ordinarily a decision requires a five-man majority), the Mobile case might have less impact.

White opponents had fewer doubts. "As of Tuesday." Mobile Commissioner Mims declared, "the federal courts are out of the minicipal affairs of Mobile, Jackson, Tuscaloosa, Gadsden and every other place waiting on the Mobile case.

"The message to federal judges is that they have usurped too much authority. They are trying to run too many local affairs.

"What Judge Pittman did was totally unAmerican, a dictatorial act on the part of a federal judge. It's high time the bureaucrats, appointees and federal judges realize that this is a government of the people."