WASHINGTON — When the Supreme Court heard arguments in December over the fate of the constitutional right to abortion, it was already clear that other rights, notably including same-sex marriage, could be at risk if the court overruled Roe v. Wade.

The logic of that legal earthquake, Justice Sonia Sotomayor predicted, would produce a jurisprudential tsunami that could sweep away other precedents, too.

The justices’ questions on the broader consequences of a decision eliminating the right to abortion were probing but abstract and conditional. The disclosure last Monday of a draft opinion that would overturn Roe, the 1973 decision that established a constitutional right to abortion, has made those questions urgent and concrete.

The opinion, by Justice Samuel A. Alito Jr., provided conflicting signals about its sweep and consequences. On the one hand, he asserted, in a sort of disclaimer that struck a defensive tone, that other rights would remain secure.

“To ensure that our decision is not misunderstood or mischaracterized, we emphasize that our decision concerns the constitutional right to abortion and no other right,” he wrote. “Nothing in this opinion should be understood to cast doubt on precedents that do not concern abortion.”

On the other hand, the logic of the opinion left plenty of room for debate.

It said a right to abortion cannot be found in the Constitution or inferred from its provisions. The same could be said, using the draft opinion’s general reasoning, for contraception, gay intimacy and same-sex marriage, rights established by three Supreme Court decisions that were discussed at some length in the argument in December.

At the argument, Justice Sotomayor sparred with Scott Stewart, Mississippi’s solicitor general, who was defending a state law banning most abortions after 15 weeks of pregnancy.

“I’m not trying to argue that we should overturn those cases,” she said of the other decisions. “I just think you’re dissimilating when you say that any ruling here wouldn’t have an effect on those.”

Mr. Stewart tried to distinguish the three other rulings from Roe, saying they were clearer, had given rise to more public reliance and did not “involve the purposeful termination of a human life.”

Justice Sotomayor was unimpressed, saying all of the cases were grounded in the same kind of constitutional reasoning. “I’m not sure how your answer makes any sense,” she said.

Justice Alito’s draft opinion is three months old, and it is all but certain that later drafts have clarified and sharpened his arguments. But the reasoning in the draft has alarmed supporters of gay rights, who say they fear that the final opinion, if it resembles the draft, could imperil hard-won victories.

“None of us are safe from the extreme anti-women and anti-L.G.B.T.Q. ideology that now dominates this court,” Sarah Kate Ellis, the president of GLAAD, said in a statement.

Justice Alito, for his part, has made no secret of his hostility to Obergefell v. Hodges, the 2015 decision on same-sex marriage. In 2020, when the court turned down an appeal from a county clerk who had been sued for refusing to issue marriage licenses to same-sex couples, he joined a statement written by Justice Clarence Thomas that called the decision at odds with the Constitution.

“In Obergefell v. Hodges,” the statement said, “the court read a right to same-sex marriage into the 14th Amendment, even though that right is found nowhere in the text.”

That is the same argument the draft opinion makes about the right to abortion. Justice Alito’s efforts to distinguish the two questions, then, may strike some as halfhearted.

The primary distinction Justice Alito drew was that there was an important moral value at issue in Roe and in Planned Parenthood v. Casey, the 1992 decision that reaffirmed its central holding.

“Roe’s defenders characterize the abortion right as similar to the rights recognized in past decisions involving matters such as intimate sexual relations, contraception and marriage,” Justice Alito wrote, “but abortion is fundamentally different, as both Roe and Casey acknowledged, because it destroys what those decisions called ‘fetal life’ and what the law now before us describes as an ‘unborn human being.’”

Justice Alito surveyed the precedents cited by Roe and Casey to justify their protection of abortion. They included ones on interracial marriage, the right of prisoners to marry, the right to live with relatives, the right to make decisions about the education of one’s children and the right not to be sterilized without consent.

He also cited two “post-Casey decisions,” Obergefell and Lawrence v. Texas in 2003, which struck down a Texas law that made gay sex a crime.

Justice Alito, a careful draftsman, then seemed to distinguish between the two sets of decisions.

“None of the other decisions cited by Roe and Casey involved the critical moral question posed by abortion,” he wrote. “They are therefore inapposite. They do not support the right to obtain an abortion, and by the same token, our conclusion that the Constitution does not confer such a right does not undermine them in any way.”

Tellingly, perhaps, that passage in the draft opinion was silent on whether its conclusion undermined the two post-Casey decisions on gay rights.

In general, Justice Alito wrote that he was wary of “attempts to justify abortion through appeals to a broader right to autonomy,” saying that “could license fundamental rights to illicit drug use, prostitution and the like.”

“None of these rights has any claim to being deeply rooted in history,” he added, a point that could be made about same-sex marriage, too.

The Biden administration, in its brief supporting the abortion providers challenging the Mississippi law, said that overruling Roe and Casey “would also threaten the court’s precedents holding that the due process clause protects other rights, including the rights to same-sex intimacy and marriage, to interracial marriage and to use contraception.”

“None of those practices is explicitly mentioned in the Constitution,” the brief said, “and most of them were widely prohibited when the 14th Amendment was adopted.”

There are limits to analyzing the reasoning of published Supreme Court opinions, to say nothing of drafts, said Michael C. Dorf, a law professor at Cornell. “Logic and syllogisms don’t carry us very far in the law,” he said.

If the draft or something like it is issued in the coming weeks, he said, “it portends big changes because it signals that the five most conservative justices are willing to court controversy on matters they care about.”

In the draft opinion, Justice Alito insisted that “we cannot allow our decisions to be affected by any extraneous influences such as concern about the public’s reaction to our work.”

Justice Thomas echoed the point in remarks at a judicial conference in Atlanta on Friday, according to news organizations present. “We can’t be an institution that can be bullied into giving you just the outcomes you want,” he said. “The events from earlier this week are a symptom of that.”

Still, the court is seldom radically out of step with public opinion, and support for same-sex marriage is high and rising.

Justice Thomas was reported to have voted with Justice Alito in the abortion case, along with the three members of the court appointed by President Donald J. Trump: Justices Neil M. Gorsuch, Brett M. Kavanaugh and Amy Coney Barrett.

Mr. Trump had vowed to name justices who would overrule Roe, and the draft opinion suggested that he is on the cusp of success. His attitude toward the same-sex marriage ruling, which his appointees may or may not share, was more accepting.

In an interview on “60 Minutes” shortly after the 2016 election, one that revealed a flexible conception of the power of precedent, he said the court should overrule Roe, which was more than 40 years old and had been repeatedly reaffirmed.

The same-sex marriage ruling, issued the previous year, was a different matter, he said.

“It’s law,” he said. “It was settled in the Supreme Court. I mean, it’s done.”