The Supreme Court's two decisions in June were finely balanced, with legal experts saying they had achieved the twin goals of advancing the cause of gay rights and avoiding a backlash in parts of the country not ready to embrace same-sex marriage.
One decision struck down the part of the federal Defense of Marriage Act that denied federal benefits to same-sex couples in states that allowed such unions. The other declined to say whether the Constitution required states to allow such marriages in the first place.
Since then, the pace of change has been rapid. When the justices heard arguments in the cases in March, same-sex marriage was permitted in nine states and the District of Columbia. If the Utah decision stands, the number of states allowing such marriages will have doubled, to 18.
On Dec. 19, the New Mexico Supreme Court allowed same-sex marriage there. And Monday, a federal judge in Ohio said the state must in at least some circumstances recognize same-sex marriages performed in other states.
Michael J. Klarman, a historian at Harvard Law School and the author of "From the Closet to the Altar: Courts, Backlash and the Struggle for Same-Sex Marriage," said he had expected rapid change — but not this rapid.
"The Utah decision is unique," he added, "because it's in a state with so much opposition to same-sex marriage. In Utah, you're going to have a real experiment in backlash."
Many hundreds of couples have gotten married there in the last week. Judge Robert J. Shelby of the U.S. District Court in Salt Lake City turned back a request to stay his decision, and a two-judge panel of the U.S. Court of Appeals for the 10th Circuit, in Denver, agreed, although it called for "expedited consideration" of the appeal.
The question for the Supreme Court in the short term will be whether to block Shelby's ruling while appeals proceed. The state's request will initially be directed to Justice Sonia Sotomayor, the member of the court responsible for overseeing the 10th Circuit, but she will almost certainly refer the matter to the full court. It is likely to act within several days.
The Supreme Court will face difficult calculations, ones it did not have to confront in reviewing decisions from federal courts in California striking down Proposition 8, the state's ban on same-sex marriage. In that case, the U.S. Court of Appeals for the 9th Circuit, in San Francisco, stayed both the trial judge's ruling and its own as appeals went ahead.
Dorf said there were probably not five votes on the Supreme Court to block Shelby's ruling. "On the strictly legal argument," he said, "it's hard to justify granting a stay."
But he added that the lower courts should have done so, partly because of the potential cruelty of voiding the new marriages and partly because the Supreme Court is hard to predict.
"It's pretty clear that even the five justices who are sympathetic to same-sex marriage would rather take a few years before getting there," Dorf wrote in a blog post on Tuesday. "If their hand is forced, as it now will be, it's impossible to say with certainty what they'll do."
Whatever the Supreme Court does regarding a stay, it is hard to see how it could hear the larger issue in the case in the current term. But a decision in the court's next term, culminating in a decision in June 2015, is entirely possible.
In the meantime, Shelby's decision will certainly get the justices' attention. He acknowledged, for starters, that the Supreme Court's 5-4 decision striking down part of the Defense of Marriage Act, United States v. Windsor, could be read to support either side in his case.
Justice Anthony M. Kennedy, writing for the majority in Windsor, said "the definition and regulation of marriage" was generally "within the authority and realm of the separate states." That would seem to suggest that voters in Utah were entitled to amend their state's Constitution to ban same-sex marriage.