By Maura Dolan

SAN FRANCISCO — Backers of gay marriage expressed satisfaction with the arguments before the U.S. Supreme Court on Tuesday, saying they believed the justices supported their position.

Jon Davidson, legal director of Lambda Legal, a gay rights advocacy group, said the hearing assured him that California gays are likely to be permitted to marry again.

He said the most devastating admission for the proponents came when Charles Cooper, the lawyer defending Proposition 8, which bans same-sex marriage in California, was asked whether there was any rational basis for treating gay people unequally in any setting, such as employment, other than in marriage. Cooper said he could not think of such think of any other setting, Davidson said.

“That was an incredibly damaging admission,” Davidson said.

He said several justices indicated doubt about whether the proponents of Proposition 8 had the legal right, or standing, to appeal a San Francisco federal court’s ruling against Proposition 8.

“I don’t know how they would rule on that. They were struggling with it. Some of them did seem concerned.”

He said Justice Samuel A. Alito Jr. appeared “very hostile” to approving same-sex marriage, and “Justice [Antonin] Scalia was scowling a lot and kind of sarcastic.”

“I think it is not very likely we will get either of their votes.”

He said he was “very encouraged” by Justice Anthony Kennedy’s expressed concern about the children of same-sex couples.

Davidson said his impression was the Supreme Court would either reject the appeal on grounds of a lack of standing by the plaintiffs or rule in some way that would overturn Proposition 8.

“I didn’t hear anything that made me think we might lose outright,” he said.

He described the arguments as “very exciting, with the justices interrupting one another as well as the counsel.”

“I rarely have seen them so engaged,” the gay rights lawyer said. “The arguments were incredibly passionate.”

Minutes after the conclusion of oral arguments in the case, Constitutional Accountability Center Vice President Judith E. Schaeffer released the following reaction:

“When pressed by the justices, the lawyer defending Proposition 8 could not come up with any legitimate reason for excluding gay and lesbian couples from the freedom to marry. The Justices, while uncomfortable with Proposition 8, seemed hesitant to rule on the merits, but as Justice Kennedy noted, there was concern about branding the families of nearly 40,000 children in California as second-class.

“One important question Justice Scalia asked former Bush Solicitor General Theodore Olson, who defended marriage equality, was when it became unconstitutional to deny gay and lesbian couples the right to marry. The answer is 1868, when the American people added the 14th Amendment’s universal guarantee of equality to the Constitution.”

The Times’ David G. Savage reported that the justices sounded closely split Tuesday, but Justice Kennedy suggested that the court should strike down the California ban without ruling broadly on the issue of same-sex marriage.

Twice during the oral argument, Kennedy questioned why the court had voted to hear the California case.  “I wonder if this case was properly granted,” Kennedy said at one point.

His comments suggested that the court’s four most conservative justices voted to hear the California case. Had the justices turned down the appeal, as Kennedy suggested, Proposition 8 would have been struck down as ruled by by the U.S. 9th Circuit Court of Appeals.