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’ll probably take the plunge — just not yet. In the meantime, though, 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, at least reading the oral-argument tea leaves, prepared to take the significant step of overturning the Defense of Marriage Act (DOMA) and granting 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, from the perspective of those supporting same-sex marriage, of making the DOMA case look like a relatively easy and modest move.

Ultimately, will a majority of the court find that the Constitution protects the right of gay and lesbian couples to marry? Maybe it’s wishful thinking, but 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?”

Actually, what Cooper thinks doesn’t matter. But if Kennedy is hearing those voices, that signals where in those uncharted waters the court may end up.

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 next day, 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.”

Indeed, as Justice Sonia Sotomayor pointed out, discriminating against same-sex couples is hardly uniform. “You are treating the married couples differently,” she said. “You are saying that New York’s married couples are different than Nebraska’s.”

Ann Telnaes animation: Another reason for diversity on the Supreme Court. (Ann Telnaes/The Washington Post)

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

Sotomayor: “Outside of the marriage context, 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.”

Likewise, 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 about wading into the issue right away. 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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