U.S. voters will be choosing not only a president Nov. 8, but also very likely the future make-up of the Supreme Court and the direction the law of the land will take on a variety of sensitive national issues.

Only two certified liberals, Justice william Brennan and Justice Thurgood Marshall, now remain on the court, and they are both over 80 years old. Brennan has served for 32 years and Marshall is in his 21st year. A third justice, Harry Blackmun, a swing vote, also is 80 and is an 18-year veteran of the court.Observers speculate that the next president will have the opportunity during the next four years to fill vacancies with new justices whose influence will be felt well into the next century.

Conservative legal experts believe a victory for Republican Vice President George Bush will open a golden era of opportunity that will reverse the direction of the high court with new rulings:

- Outlawing abortion.

- Easing restraints on the police in the conduct of investigations, the use of intrusive devices for the surveillance of citizens, searches and seizure of evidence and the treatment of criminal suspects, and making easier the imposition of the death penalty.

- Barring gender and racial preference in hiring to redress to past discrimination.

- Relaxing church-state prohibitions against aid to parochial schools.

- Resurrecting theories of property rights that would require government to compensate businesses for losses or costs resulting from compliance with laws like those requiring landlords to rent to families with children or install special facilities for the handicapped.

"With a more conservative court, one could anticipate more drug testing in the work place, perhaps an end to rent control and burdens on employers, like maternity leave," says Bruce Fein, who served as an associate deputy attorney general during President Reagan's first term and who writes on constitutional issues.

President Reagan's efforts over eight years to move the court to the right were only partly successful. He nominated, and the Senate confirmed, three justices to the nine-member bench. They are Sandra Day O`Connor, 58, the first woman to sit on the high court, who has disappointed conservatives on some issues; Antonin Scalia, 52, who has delighted them on most issues; and Anthony Kennedy, the newest addition to the high court, who came with conservative credentials but has not yet established a track record.

Of the remaining members of the court, Justice John Paul Stevens, 68, is an unpredictable swing vote; Justice Byron White, 71, has moved steadily to the right during his tenure, and Chief Justice William Rehnquist, 63, is still regarded as very conservative, despite some recent rulings that surprised the right wing.

The court is now narrowly divided, 5-4 in favor of the conservative position on many - but not all - issues. In general, the court is already progressing in the direction the conservatives want it to go - but at "adagio pace," Fein says.

Patrick McGuigan, a constitutional scholar at the conservative Free Congress Center for Law and Democracy, sees fewer areas for a dramatic transformation in the court than Fein forecasts.

McGuigan predicts vacancies on the court would come more quickly if Democrat Dukakis is elected. He reasons that the court's aging liberals will step down to give the Massachusetts governor the opportunity to "lock in a committed liberal minority."

Dukakis' replacements would be "young, vigorous intellectually and smart, able to reach out reach out frequently to John Paul Stevens, and sometimes capture a Sandra Day O`Connor and so forth," McGuigan says.

That would leave the conservatives with a very tenuous majority indeed.