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Same-sex marriage proponents are gathering steam.

Recent high profile rulings on gay marriage tell only part of the story about the avalanche of lawsuits working their way through state and federal courts, challenging laws that ban or restrict same-sex marriages.

Cases are now pending in all but eight of the 33 states that forbid gay couples to marry. Most have been filed since the U.S. Supreme Court ruled last June that the federal government cannot refuse to recognize same-sex marriage in the states where it's legal.

"Because of that decision, the dam burst," said Jon Davidson, legal director of Lambda Legal, a gay rights organization that has been active in litigating the issue.

Though the justices said nothing in June about whether a state must allow gay couples to marry, the language of their ruling, which found "no legitimate purpose" in declaring same-sex marriages less worthy, has been cited repeatedly in lawsuits attacking gay marriage bans and in court decisions declaring them invalid.

"People began to see that the chances of success in court were greater. And being able to marry became even more important in terms of whether couples would get rights under federal law," Davidson said.

Soon after the Supreme Court ruling, gay rights groups began planning their legal strategies, focusing on states where further victories seemed the most likely. Utah was not high on the list, but a federal judge there in late December struck down the state's constitutional amendment barring same-sex marriage.

That was followed rapidly by similar rulings in Oklahoma and Virginia. Utah and Oklahoma are challenging the decisions, and the 10th Circuit Court of Appeals will hear the cases in mid-April.

"Because of that [Supreme Court] decision, the dam burst."

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Judges in Ohio and Kentucky have issued more limited rulings, requiring recognition of marriages legally performed elsewhere.

Opponents of same-sex marriage have achieved some victories. In Nevada, a federal judge in 2012 rejected a challenge to that state's ban. The 9th Circuit Court of Appeals will soon hear arguments in the case, but the state's attorney general dropped out of the case earlier this month, citing a ruling in a separate case that undercut the state's legal reasons for defending the ban.

State attorneys general in Oregon, Pennsylvania, and Virginia have also declined to defend their laws, concluding that bans in their states are unconstitutional.

By contrast, Michigan Attorney General Bill Schuette, is defending his state's ban, which goes on trial in federal court in Detroit beginning Feb. 25.

"Michigan supports natural procreation and recognizes that children benefit from being raised by parents of each sex who can then serve as role models of the sexes both individually and together in matrimony," says a brief filed by the state.

Texas officials urged a federal court to uphold their state's ban during a federal court hearing on Feb. 12. An assistant Texas solicitor general, Mike Murphy, called the legalization of same-sex marriage "a more recent innovation than Facebook."

The issue is also pending before the Texas Supreme Court. It heard arguments in November in two cases brought by same-sex couples who were legally married in Massachusetts but seek to have their marriages recognized by Texas so they can file for divorce.

"Proponents will keep coming until they get what they want — a national mandate of same-sex marriage."

It seems a near certainty that the issue will be back at the U.S. Supreme Court soon, either by the next term that begins in October or the year after.

"Once you start having so many states under federal court order to marry same-sex couples and cases come out all over the place, I think the court faces a lot of pressure to resolve the question," said Paul Smith, a Washington, DC lawyer who argued the landmark Texas gay rights case before the justices in 2003.

"You start having a lot of displacement of state law. They may find they cannot delay any longer."

Austin Nimocks of the Alliance Defending Freedom, a group that opposes marriage for gay couples, says the number of lawsuits is no surprise. "Proponents will keep coming until they get what they want — a national mandate of same-sex marriage."

But he says even a Supreme Court ruling won't settle the matter. "The court is not going to decide the issue of same-sex marriage for anybody. The issue will ultimately belong to the people."

A total of 17 states now permit same-sex marriage. Twenty-nine ban it by state constitutional amendment. The other four forbid it by statute.

Of the 33 states barring marriage for gay couples, lawsuits have been filed in all but Alaska, Georgia, Indiana, Montana, Nebraska, North and South Dakota, and Wyoming.