Listening to the Supreme Court hear arguments in the same-sex marriage cases was like watching a novice diver inch to the edge of the high board for the first time.

Eventually, she may take the plunge - just not yet. But she can execute an impressive maneuver from lower heights.

In other words, the justices seemed tempted to put off deciding the question of a constitutional right to same-sex marriage. But they appear prepared to overturn the Defense of Marriage Act and grant full federal benefits to same-sex couples in states that recognize their marriages.

Indeed, the juxtaposition of the two cases may have the beneficial effect of making the DOMA case look like a relatively modest move.

Ultimately, will a majority of the court find that the Constitution protects the right of gay couples to marry? The comments in Tuesday's arguments on California's Proposition 8 suggested the possibility of a skittish, tenuous majority inclined toward finding a right.

Justice Anthony M. Kennedy, the likely swing vote, worried openly about the court being asked "to go into uncharted waters." But, he told Charles Cooper, who was defending the ban, "there are some 40,000 children in California" who "want their parents to have full recognition and full status. The voice of those children is important in this case, don't you think?"

The two days of oral argument underscored how difficult it is for opponents of marriage equality to concoct a convincing case for limiting marriage to opposite-sex couples. Cooper was reduced to citing the state's supposed interest in "responsible procreation," within the context of marriage.

Yet as Justice Elena Kagan pointed out, this rationale explains why same-sex couples might not be included in the definition of marriage - it doesn't provide a basis for excluding them, any more than couples too old to have children could be barred from marrying.

The argument from Paul Clement, supporting DOMA on behalf of Republicans in the House of Representatives, boiled down to the alleged federal need for "uniformity" in administering benefits.

Again, Kagan: "Historically, the only uniformity that the federal government has pursued is that it's uniformly recognized the marriages that are recognized by the state."

The arguments also illustrated how far the legal and political debate on gay rights has come. Just 27 years ago, the court - in a case since overturned - ruled that states could, consistent with the Constitution, criminalize homosexual conduct. At the Prop. 8 arguments, Cooper - the lawyer for the anti-gay-rights side - took pains to make clear how much his argument was limited to matters of marriage.

Justice Sonia Sotomayor: "Can you think of any other rational basis … for a state using sexual orientation as a factor in denying homosexuals benefits or imposing burdens on them? … Denying them a job, not granting them benefits of some sort, any other decision?"

Cooper: "Your honor, I cannot."

In the DOMA case, Chief Justice John Roberts, seeking to head off the claim that laws discriminating on the basis of sexual orientation should be subject to heightened scrutiny by courts, cited the increasing political power of gays and lesbians.

"As far as I can tell, political figures are falling over themselves to endorse your side of the case," he told Roberta Kaplan, representing Edith Windsor, a New York woman who had to pay an extra $300,000 in extra estate taxes after her spouse died.

As Justice Samuel Alito noted in the Prop. 8 case, the court is being asked to render judgment "based on an assessment of the effects of this institution which is newer than cellphones or the Internet." That explains the court's understandable edginess.

But, like cellphones and the Internet, same-sex marriage is here to stay - and destined to be back before the high court.

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