WASHINGTON » President Barack Obama has balanced on a political tightrope for two years over the Defense of Marriage Act, the 1996 law barring federal recognition of same-sex marriages. Now, two new federal lawsuits threaten to snap that rope out from under him.

Obama, whose political base includes many supporters of gay rights, has urged lawmakers to repeal the law. But at the same time, citing an executive-branch duty to defend acts of Congress, he has sent Justice Department lawyers into court to oppose lawsuits seeking to strike the law down as unconstitutional.

The two lawsuits, however, have provoked an internal administration debate about how to sustain its have-it-both-ways stance, officials said. Unlike previous challenges, the new lawsuits were filed in districts covered by the appeals court in New York — one of the only circuits with no modern precedent saying how to evaluate claims that a law discriminates against gay people.

That means that the administration, for the first time, may be required to take a clear stand on politically explosive questions like whether gays have been unfairly stigmatized, are politically powerful and can choose to change their sexual orientation.

"Now they are being asked what they think the law should be, and not merely how to apply the law as it exists," said Michael Dorf, a Cornell University law professor. "There is much less room to hide for that decision."

James Esseks, an American Civil Liberties Union lawyer helping with one of the new cases, said the new lawsuits could be game-changing.

The Obama legal team has not yet decided what path to take on the lawsuits, according to officials who spoke on condition of anonymity about the internal deliberations. But the Justice Department must respond by March 11. The debate has arisen at a time when Obama has signaled that his administration may be re-evaluating its stance.

As a candidate, Obama backed civil unions for gays while opposing same-sex marriage. But last month, after Congress — in the final hours before Republicans took control of the House — repealed the law barring gays from serving openly in the military, Obama told The Advocate, a magazine the focuses on gay issues, that his views on marriage rights "are evolving."

"I have a whole bunch of really smart lawyers who are looking at a whole range of options," he said, referring to finding a way to end the Defense of Marriage Act. "I’m always looking for a way to get it done, if possible, through our elected representatives. That may not be possible."

Since 2003, when the Supreme Court struck down laws criminalizing gay sex, the legal landscape for same-sex marriage has altered dramatically. Eight states now grant marriage licenses to same-sex couples or recognize such marriages if performed elsewhere. But under the Defense of Marriage Act, the federal government cannot recognize those relationships.

That has raised a crucial question: Is it constitutional for the federal government to grant certain benefits — like health insurance for spouses of federal workers, or an exemption to estate taxes for surviving spouses — to some people who are legally married under their state’s laws, but not to others, based on their sexual orientation?

The Constitution declares that everyone has a right to equal protection by the law. But many laws treat some people differently than others. Courts uphold such policies as constitutional if they can pass a test showing that the discrimination is not invidious.

A law targeting an ordinary class — like owners of property in a district with special tax rates — gets an easy test. It is presumed valid, and a challenge is dismissed unless a plaintiff proves that the law advances no conceivable rational state interest.

But a law targeting a class that has often been subjected to unfair discrimination — like a racial group — gets a hard test. It is presumed invalid and struck down unless the government proves that officials’ purpose in adopting the law advances a compelling interest.

Gay-rights groups contend that the marriage act ought to be struck down under either test. Last year, a federal judge in Massachusetts agreed, saying it was unconstitutional even under the easy test’s standards.

But the Obama administration, which appealed that ruling, contends that a plausible argument exists for why the act might be constitutional. Justice Department officials say they have a responsibility to offer that argument and let courts decide, rather than effectively nullifying a law by not defending it.

Justice officials have argued that the marriage act is justified, under the easy test’s standards, by a government interest in preserving the status quo at the federal level, allowing states to experiment. And in its brief appealing the Massachusetts ruling, the department stressed seven times that a "binding" or "settled" precedent in that circuit required the easy test.

But for the new lawsuits, no such precedent exists. The Obama team has to say which test it thinks should be used. Courts give a class the protection of the hard test if it has been unfairly stigmatized and if its members can choose to leave the class, among other factors. By those standards, it could be awkward, especially for a Democratic administration, to proclaim that gays do not qualify for it.

But under a hard test, the administration’s argument for upholding the marriage law would be weaker, legal specialists say, in part because when lawmakers enacted it in 1996, they mentioned only in passing an interest in preserving the federal status quo as states experimented.

Some conservatives have accused the administration of throwing the fight by not invoking other arguments, like morality. And in particular, lawmakers’ primary focus in 1996 was "encouraging responsible procreation and child-rearing."

But the administration’s filings in other cases disavowed that rationale, noting that infertile heterosexuals may marry and citing studies that children raised by same-sex parents are as likely to be well-adjusted as those raised by heterosexuals.

M. Edward Whelan III, a former Bush administration lawyer, said the Obama team’s rejection of the children-based rationale amounted to "sabotage." Another possible path, legal specialists say, would be to urge the judges to adopt the easy test because courts elsewhere have done so, without laying out any full legal analysis of how to think about gay people as a class.

Gay-rights supporters, however, call that option dishonest: Those cases largely derived from decisions before the Supreme Court’s 2003 sodomy ruling. The premise that it was constitutional to criminalize gay sex short-circuited appraisal of protections for gays from lesser forms of official discrimination.

"We think there is only one answer the government and the court can come to if they apply the test conscientiously, and that is that the government must have to prove why it needs to treat gay people differently," Esseks, the ACLU lawyer, said.

"And if the government has to have a real reason, as opposed to a made-up reason, we don’t think there is any way that the government wins."

© 2011 The New York Times Company