DENVER -- With its recent string of high-profile victories in federal court, the gay marriage movement is hoping to build momentum to help it attain its long-held goal: a Supreme Court decision legalizing same-sex marriage nationwide.
But first it must convince federal appellate courts of the merits of the case.
That quest begins Thursday in Denver and continues next week when a three-judge panel will hear arguments on whether they should uphold separate rulings by two federal judges that threw out same-sex marriage bans in Utah and Oklahoma.
They do so, however, in a climate far different than 2004, when voters overwhelmingly approved the prohibitions in both states.
After the U.S. Supreme Court last year ruled that a law forbidding the federal government from recognizing same-sex marriages was unconstitutional, eight federal judges in all have struck down state bans on gay marriage or on the recognition of same-sex marriages from other states.
As the panel of the 10th Circuit Court of Appeals considers the Utah case Thursday, experts say pressure is on the judges at a time when polls suggest a majority of Americans back same-sex unions.
"The challenge for a conservative judge would be: Do you want to be the only court of appeals that upholds discrimination that the country is rapidly galloping to renounce?" William Eskridge, a law professor at Yale University, said.
Opponents say that shouldn't factor into the judges' calculations.
"There are strong political factors that seem to be driving these district court decisions," said Ed Whelan of the Ethics and Public Policy Center in Washington, D.C., adding that expectations that the Supreme Court will ultimately find that gays have the right to marry may also feed into it.
"It's not the job of lower courts to predict where the Supreme Court will go," he said.
Despite the legal momentum, attorneys say it is distinctly possible the 10th Circuit could rule against gay marriage backers and argue the issue is best settled at the ballot box.
"It's an institutional argument that we've seen at the Supreme Court and we've seen in state litigation," Douglas NeJaime, a law professor at the University of California, Irvine, said.
The three judges were picked randomly to hear the case, and next week's appeal of the ruling that struck down an Oklahoma gay marriage ban, include two Republicans and one Democrat.
Kenneth Upton, an attorney with the Lambda Legal Defense Fund who watches the 10th Circuit carefully, said the panel is a perfect representation of a court that is generally moderate and centrist.
It will likely be months before the panel issues a ruling, which will become law in the six states in its jurisdiction unless it is stayed. Those states are Colorado, Kansas, New Mexico, Oklahoma, Utah and Wyoming. New Mexico's Supreme Court has already legalized gay marriage in that state.
Even if the panel upholds the lower court's decision, the argument will only be settled when it moves one more level up to the Supreme Court.
Still, both sides say the stakes are high on Thursday.
"Having a victory from the 10th Circuit would be electrifying," said Shannon Minter, legal director for the National Center for Lesbian Rights, which is representing the plaintiffs in the Utah case.
Jim Campbell, an attorney for Alliance Defending Freedom, which represents religious organizations, said: "The stakes are whether the people can continue to define marriage as between a man and a woman."
Lawyers for Utah and several other organizations that have filed briefs supporting the state's side argue the ban should stand because the state has a right to promote marriage between a man and a woman, which is optimal for child rearing.
The plaintiffs and gay rights proponents counter there is little data backing up the state's case on parenting and that the ban improperly deprives gay couples of the right to marriage.
The rapid pace of lawsuit filings against same-sex marriage bans continued Wednesday with a suit in North Carolina.
Andrew Koppelman, a law professor at Northwestern University, said that societal change has made the final outcome inevitable.
"I don't know what's going to happen in this case, but it's clear that the same-sex marriage movement has won," Koppelman said.