SAN FRANCISCO  In all of the legal maneuvering surrounding the challenge in federal court to Proposition 8, California’s 2008 voter-approved ban on same-sex marriage, one thing has seemed all but certain: the case would eventually head to the Supreme Court.

But that trip could come  in a way  as soon as this week, as proponents of the ban seek to prevent a resumption of same-sex marriages. Judge Vaughn R. Walker of Federal District Court, who this month ruled Proposition 8 to be unconstitutional, lifted a temporary stay on his decision on Thursday, but allowed six days for a three-judge panel of the United States Court of Appeals for the Ninth Circuit to review it.

Some legal experts are skeptical of whether the Ninth Circuit panel  made up of two Democratic appointees and a moderate Republican  will intervene. And so it is that proponents may find themselves heading to the Supreme Court to try to obtain an emergency stay.

It is at that level that proponents, who are on a legal losing streak, may find some relief, experts say.