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WASHINGTON -- As partisans argued pointedly over same-sex marriage outside the U.S. Supreme Court building, either hoping for or dreading a landmark decision, justices inside seemed reluctant Tuesday to extend a sweeping constitutional right for gays and lesbian to wed in all 50 states.
In the first of two days of hearings on cases that have the potential to fundamentally alter how American law treats marriage, Justice Anthony Kennedy -- considered the likely deciding vote on the divided court -- questioned whether justices should even be hearing the issue.
"This was a deeply divided Supreme Court, and a court that seemed almost to be groping for an answer here," said CNN Senior Legal Analyst Jeffrey Toobin, who watched the arguments over California's Proposition 8, which bans same-sex marriage.
Voters approved the proposal 52% to 48% in November 2008, less than six months after the state Supreme Court ruled that marriage is a fundamental right that must be extended to same-sex couples.
The court will listen to arguments Wednesday on a separate challenge to the federal Defense of Marriage Act, which -- like the California law -- defines marriage as between a man and a woman.
The overriding legal question in the California case is whether the 14th Amendment guarantee of equal protection under the law prevents states from defining marriage as that state has.
Regarding allowing same-sex couples to marry, Justice Elena Kagan, a liberal member of the court, asked, "What harm is there to the institution of marriage?"
But more conservative members of the court took a go-slow approach. Justice Samuel Alito said the law on same-sex marriage is too new.
"There isn't a lot of data on its effect" on children and the institution of marriage, he said.
While the justices were clearly torn on the larger constitutional questions, they may be poised to dismiss the appeal on jurisdictional grounds.
A key question is whether the private citizens who put Proposition 8 on California's ballot have standing to defend it in court when the state's governor and attorney general have refused to do so.
If the court dismisses the appeal on those grounds, it might mean lower federal court rulings declaring the proposition unconstitutional would stand.
But it wouldn't allow for a broader, final rule outlining the power of states to say who can or can't get married.
Kennedy admitted the law's supporters are "not just any citizens."
But he later raised concerns about whether the possibility of same-sex marriage was enough to establish they had suffered harm, a key jurisdictional hurdle allowing them to appeal in the first place.
Justice Sonia Sotomayor said it is the state's responsibility -- through its elected leaders -- to defend laws in court, and that private individuals could not establish "how their injury was separate from everyone else."
Attorneys who represented the two couples seeking to overturn Proposition 8 said they couldn't tell how the court would rule.
"We are confident where the American people are going with this," said Theodore Olson. "We don't know for sure what the United States Supreme Court is going to do, but we're very, very grateful they listened, they heard, they asked hard questions, and there's no denying where the right is."
Andrew Pugno, general counsel for the Protect Marriage Coalition, the group defending Proposition 8, said their attorney had "credibly presented the winning case for marriage."
"We think the hearing went very well," he told reporters.
Two of the key plaintiffs are Paul Katami and Jeff Zarrillo, a Burbank, California, couple who want to marry but can't because of Proposition 8. They say the state is discriminating against them for their sexuality.
"It's as simple as that," Katami said after the hearing. "It's our constitutional right and I cannot wait to start my family with Jeff."
The court is unlikely to announce its decision until June.
During Tuesday's arguments, supporters of same-sex marriage rallied outside the Supreme Court, hoping justices would reach for a broad ruling that would strike down bans nationwide.
"We are not asking for anything more than our neighbors, friends and family, but certainly expect no less," said Todd Bluntworth, who spoke with his husband and their two children to a crowd of supporters hoping for a historic ruling from the Supreme Court striking down laws banning same-sex marriage.
But opponents who rallied nearby urged the court to keep out of the issue and leave the decision to states.
"If you want to get married, go to one of the states that allows gay marriage," said Carl Boyd Jr., a conservative Nashville talk-show host. "Stop trying to force your agenda down our throats. Quit trying to bully the American people with the homosexual agenda."
Some demonstrators carried sign reading "Kids do best with a mom & dad."
Patchwork state laws
If the court decides in their favor, it would mark
a historic shift in how the law treats marriage, striking down laws across the country banning same-sex marriage and matching an apparent cultural shift toward acceptance of same-sex couples.
Or the court could leave the current patchwork of state laws in place, choosing to let state legislatures and state courts sort it all out.
Forty-one states now forbid same-sex marriage, although nine of them allow civil partnerships. Nine other states allow same-sex marriage, and about 120,000 same-sex couples have gotten married, according to estimates.
California's ban seem to run counter to polls that show rising support overall for same-sex marriage. A CNN/ORC International poll released Monday found that 53% of Americans now support same-sex marriage, up from 40% in 2007.
California Attorney General Kamala Harris, who is arguing against Proposition 8, said voter-approved marriage bans "are simply unconstitutional."
The Supreme Court has ruled more than a dozen times that marriage is a fundamental right, "and as it relates to a fundamental right, the court will hold that under the highest level of scrutiny," Harris said.
The Defense of Marriage Act bars the federal government from recognizing state-sanctioned same-sex marriages. It prevents legally married gay and lesbian couples from getting federal benefits and privileges, like tax breaks and survivor benefits, that are extended to opposite-sex married couples.
Partisans speak out
Same-sex marriage supporters say it's time for the court to take a stand that puts all Americans on the same footing.
"This is about our equality," Katami said. "This is about our freedom and our liberty. So we are not trying to topple marriage. We are not trying to redefine marriage. What we are trying to say is that equality is the backbone of our country."
But supporters of Proposition 8 and DOMA say the Supreme Court should stay out of the issue and let voters decide what they want.
"Our most fundamental right in this country is the right to vote and the right to participate in the political process," said Austin Nimocks of the Alliance Defending Freedom, a Christian advocacy group.
"We don't need the Supreme Court to take that right away from Americans of good faith on both sides of this issue and impose its judicial solution," Nimocks said. "We need to leave this debate to the democratic process, which is working."
The Obama administration has formally expressed support for same-sex marriage in California, weighing in on the case in a brief last month. Obama, whose views on the issue have changed over his political career to full support, said he would vote to strike down the state's law if he sat on the court.
In what some have labeled the "nine-state strategy," the Justice Department argument is expected to center on the idea that civil union and domestic partnership laws may themselves be unconstitutional and that those states should go all the way and grant same-sex couples full marriage rights.
Other prominent politicians have expressed timely opinions in recent weeks, indicating the importance of the matter in the social context of 21st century American politics.
Hillary Clinton, the former secretary of state and possible 2016 Democratic presidential candidate, recorded a video for a gay rights group indicating her support.
Republicans have described cracks appearing in their party's long-held opposition to same-sex marriage.
"There is no putting this genie back in the bottle. It is undeniable. The shift is here and we're not going back," Republican strategist and CNN contributor Ana Navarro said Sunday.
One prominent Republican, Sen. Rob Portman of Ohio, endorsed that shift this month, two years after his son revealed to him that he is gay.
The case being heard Tuesday is Hollingsworth v. Perry (12-144), dealing with Proposition 8. And coming up Wednesday is U.S. v. Windsor (12-307), which deals with the DOMA issue.
Bill Mears reported and wrote from Washington, Michael Pearson reported and wrote from Atlanta; CNN's Joe Johns, Alan Duke and Samira Jafari contributed to this report.