DENVER (AP) -- The gay rights movement's winning streak in same-sex marriage lawsuits faces its biggest test yet in Denver where a federal appeals court will weigh whether to give an important victory to gay couples' right to marry or halt their momentum.
A three-judge panel will hear arguments on Thursday and next week 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 show a majority of Americans backing same-sex unions.
"The challenge for 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?" said William Eskridge, a law professor at Yale University, said. "The handwriting is on the wall."
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. "If the court wanted to not say something about the merits, but uphold the ban, they could go that direction."
The three judges 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.
One of the Republicans, Jerome A. Holmes, appointed by President George W. Bush, initially voted against staying the trial court's ruling, which allowed more than 1,000 gay couples to wed in Utah in December before the Supreme Court stepped in and stayed the initial ruling.
The other two judges are Carlos F. Lucero, appointed by President Bill Clinton, and Paul J. Kelly, Jr., appointed by President George H.W. Bush.
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.
"If you wanted to pick a panel where you could do a straw poll of the judiciary, this is a pretty good sample," Upton said.
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. The high court could get a case either from the 10th circuit or one of the at least four other appeals courts scheduled to consider the issue.
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. "It would be extremely encouraging and help continue the incredible momentum."
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 childrearing.