Activists on both sides of the volatile national debate over abortion say the Supreme Court, in accepting a key case from Pennsylvania, is poised to undermine the constitutional right it established 19 years ago Wednesday.

The court's timing - a decision is expected by July - likely will ignite a political powder keg in the midst of the 1992 campaign season."One of two things will happen and either will be good," said Douglas Johnson of the National Right to Life Committee. "They may use this case to re-examine and overturn Roe. Or they may stop well short of that but still uphold the Pennsylvania law's provisions."

"The days of safe, legal abortion are now numbered," said Kate Michelman of the National Abortion Rights Action League.

The justices said Tuesday they will rule on the Pennsylvania law, substantially upheld by a federal appeals court, that restricts women's access to abortions.

At least five of the justices have indicated a willingness to allow states to place some restrictions on that access. The question is whether they will use the Pennsylvania case to reverse the 1973 Roe vs. Wade ruling that made abortion legal.

President Bush has called for a reversal, and the Republican party's 1988 platform included a strong "pro-life" anti-abortion statement.

Abortion rights advocates believe a decision reversing Roe vs. Wade would spark a "pro-choice" backlash in this year's elections. But they also fear that a murky ruling might gut the 1973 decision without saying so directly, leaving voters confused.

There is widespread agreement among activists on both sides that the court's decision will make abortions more difficult to obtain - even if the court stops short of overturning Roe vs. Wade.

Georgetown law professor Susan Low Bloch said she doubts that the court would use its review of the Pennsylvania law to reverse Roe vs. Wade because "the case doesn't require it."

"There are cases from Guam, Utah and Louisiana that will reach the court in which revisiting Roe will be unavoidable," she said. "I don't think the court wants to reach out unnecessarily in this case. The way review was granted confirms that intuition."

Harvard law professor Laurence Tribe also predicts the court "may well avoid the ultimate issue" and instead adopt a new standard under which "most restrictions enacted by the states would be allowed."

At issue are provisions in the Pennsylvania law that, among other things, require:

-Doctors to tell women seeking abortions about fetal development and alternatives to abortion.

-Women to put off an abortion for 24 hours after receiving such information.

-Doctors to keep detailed information, subject to public disclosure, on all abortions performed.

-Minors under 18 years old to first get one parent's consent or judicial approval.

-Married women to tell their husbands about a planned abortion.

Except for spousal notice, the 3rd Circuit U.S. Court of Appeals upheld all of the provisions.

In 1986 the Supreme Court struck down virtually identical Pennsylvania regulations, but since then the court's cast has changed.