"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.
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 Supreme Court sounded skeptical of the childrearing argument in its ruling last year, noting that gay couples raise children who are harmed by their parents' marriages not being recognized.
Underscoring the political pressure in the case, a pro-gay marriage group began airing ads supporting same-sex weddings in Colorado, Oklahoma, Wyoming and Washington, D.C., on Tuesday.
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. "Federal judges know that. You bring these cases before them, and they don't want to say 'No.'"
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