The clearest message from the Supreme Court this year is how important the presidential election is.

For when the court addressed the major social issues -- the ones millions care about -- its answers came most of the time by margins of no more than a single vote. And with five of the nine justices over 70 years old, to the victor in November probably belongs a court majority.

If the court term that concluded Wednesday is any indication, the new president will find hanging in the balance these issues -- school busing, abortion funding, aid to private schools, genetic engineering, protection from cancer-causing chemicals, voting rights, prisoner rights, prisoner rights and, possibly, the implementation of death penalty laws, among other things.

The fact that the court was so closely divided almost guarantees that these issues will return during the next four years.

Narrow margins at the court and legal reasoning muddled by divisions encourage new lawsuits, some lawyers say, and leave lower-court judges uncertain on how to decide them.

So once again this year, if there was any theme in the 1979-1980 Burger court, it was the lack of a theme. If there was a conservative victory, there was a liberal victory closely on its heels to balance it. If there was a dissent by William H. Rehnquist on one case, one could count on a dissent by William J. Brennan Jr. or Thurgood Marshall in the immediate future.

Others were less predictable. There was Chief Justice Warren E. Burger, a supposed enemy of the press, making himself the media champion in his decision on open trials.

There was Justice Harry A. Blackmun, once known as a carbon copy of Burger ("Hip Pocket Harry"), decrying prison conditions and justifying a convict's decision to escape from them.

And there was Justice John Paul Stevens, considered a liberal on many issues, siding with Rehnquist on the issue of affirmative action. Congress' minority public works set-aside, he suggested, was a patronage rip-off by the Congressional Black Caucus. They wanted a "piece of the action" for their constituents, Stevens implied, contracts for political allies. And that, he said, is a "plainly impermissible justification" for a racial quota.

So as an ideological matter, neither the ACLU nor the Conservative Caucus should consider the year a failure.

The court did narrow the controversial "exclusionary" rule in some instances, giving police and prosecutors more leeway to use illegally obtained evidence at trial.

On the other hand, the justices also extended the reach of the civil rights laws deeper into local and state affairs than ever before. The court held that damage suits could be brought against state and city officials and cities themselves under federal civil rights law, not just for constitutional violations of rights but for violations of any federal law. So for those who feared a "dismantling" of the Earl Warren era, it did not happen.

Pity, however, the judges on the lower courts and state legislators who who have to decide what laws and decisions the high court will deem proper. The court issued 129 opinions this term. Of those, maybe 50 were of significant social importance: abortion, race and genetic engineering, for obvious examples.

Of those, roughly 35 -- more than half -- reflected one-vote majorities or pluralities on the reasoning behind the judgment, if not the judgment itself.

According to American Enterprise Institute Supreme Court analyst Bruce Fein, who has studied the voting patterns, this compares with 11 one vote majorities or pluralities during the final year of the Warren court.

The change of a single vote could have turned the decision to deny poor women a constitutional right to abortion funding. A single vote could have kept the Occupational Safety and Health Administration from losing what appeared to be much of its power to enforce limits on exposure to cancer-causing benezene. One vote would have meant that genetically engineered life forms could not be patented, denying industry a major incentive in the much-feared experimentation in that field.

On school busing, the court appeared so closely split that the justices were unwilling to accept a single major case. In one instance, without explanation, the justices withdrew their earlier decision to consider busing in Dallas. In another, the court declined a significantt case from Wilmington even though there were the four votes required to consider it.

Stevens, whose former law partner was involved in the case, did not participate in the decision. Burger withheld the fourth vote, even though he said the case should be considered, because he felt a full court was required to decide it.

The impact of these decisions is inevitable. Lower court judges, without guidance, go their own way. Lawyers uncertain whether they can win or lose a case, bring it to court to find out.

"Whole categories of the law are in a shambles," said analyst Fein. "Judges are saying, 'Oh my God, what does this mean?' The court's approach can only be described as 'benign neglect' of the law."

Take, for example, the case involving the way Mobile, Ala., elects its government. A lower court judge had ordered it changed from an at-large election system to a ward system, principally because no blacks had ever been elected. The critical issue was whether, before doing this, the judge should have found that Mobile intended to exclude blaks when it set up the at-large system.

The Supreme Court resolved the issue this way: four justices said intent must be proven. Three justices said it didn't have to be. Two justices largely skipped over the question of intent and dealt with other issues on their own. Six justices voted to send the case back to the lower court judge for reconsideration.

He still does not know whether intent must be proven, however.

In a recent speech, Justice Lewis F. Powell Jr. took issue with criticisms that the court is "leaderless and unpredictable," and defended its current divisions, suggesting that the court should be a marketplace of ideas.

"I have wondered whether those who decry the "rudderless court' would like to be judged by a different kind of court. If, for example, one's liberty were at stake, would he like to be judged by a court whose members were dominated by a willful chief justice? And what confidence could a litigant have in a court that decided cases according to some consistently applied philosophy or 'theme' rather than on the facts of his case and the applicable law?"

Increasingly, however, internal concern about the confusion is surfacing in private conversations with some justices and even in opinions.

Burger recently suggested that one of the court's rulings -- one attempting to define interrogation -- would be meaningless to police and judges alike.

Blackmun marveled in the Richmond newspapers case at how a court that closed trials on July 2, 1979 -- using the world "trials" repeatedly in its opinion -- could on July 2, 1980, suddenly open them up.

What may be a nightmarre for lower judges and lawyers, however, is an opportunity for the next president.

For the one unalterably common feature of a court's majority is its age: Blackmum, Burger, Marshall, Brennan and Powell are all over age 70.

And here are some of the other decisions with one-vote margins or pluralities on major questions:

A ruling that city governments cannot defend themselves aainst civil rights suits simply by pleading "good faith" -- that they were just doing their job (Owen vs. City of Independence).

A ruling allowing New York state to give a limited type of aid to parochial schools for state-mandated testing and pupil attendance reporting (Committee for Public Education vs. Regan).

A ruling upholding a habitual-offender statute that resulted in a life prison term for a man convicted of taking about $130 (Rummel vs. Estelle).

A ruling that college professors at Yeshiva University are "management" and not protected by collective bargaining laws (NLRB vs. Yeshiva).

A decision overturning a law allowing prior restraint to be imposed on pornography films. (Vance vs. Universal Amusementt Co. Inc.)

A ruling allowing corporations to use monopoly tactics to protect new uses for old but unpatented chemicals (Rohm and Haas vs. Dawson).

A decision potentially freeing unions from an administrative ruling making it more difficult to preserve jobs in the face of automation (NLRB vs. ILA).