WASHINGTON (CNN) — The Supreme Court heard arguments for almost two hours Wednesday on a challenge to the Defense of Marriage Act, a law that denies equal federal benefits permitted in states where same-sex marriage is legal.

The arguments concluded presentations before the high court on one of the most prevalent social issues of this era — the right of gay and lesbian couples to wed and receive the full benefits of law provided to heterosexual couples.

Wednesday’s case examined the practical impact of the 1996 act, which defines marriage as between a man and woman and therefore means federal tax, Social Security, pension and bankruptcy benefits as well as family medical leave protections do not apply to legally married gay and lesbian couples.

It involves Edith “Edie” Windsor, who was forced to assume an estate tax bill much larger than a surviving spouse in a heterosexual marriage would have to pay.

Because her decades-long partner was a woman, the federal government did not recognize their same-sex marriage in legal terms, even though their home state of New York did.

“I was devastated by the loss of the great love of my life, and I was also very sick, then had to deal with pulling together enough money to pay for the taxes,” the 83-year-old Windsor recently told CNN.

Outside the court, public interest remained high, but not at the same level as Tuesday’s arguments in another case involving California’s voter-approved ban of same-sex marriage.

A smaller crowd gathered than the day before, with most of them opponents of the Defense of Marriage Act.

“I’m here today because I’m a social worker and I’ve seen a lot of people suffer over the years,” Mary Ann Piet told CNN. “And I’m concerned about not getting people their human rights, their dignity as people.”

Asked what she hoped to hear Wednesday, Piet said she wanted the justices to show that “they are going to think it through carefully” and determine that “we all deserve the same” to “fit with what the United States stands for.”

Conservative supporters of the law, known by its acronym of DOMA, contend it codifies a fundamental cornerstone of society, and changing the definition of marriage would have widespread negative impacts.

The federal statute presents tricky gateway or “standing” questions that threaten to stall any final consideration of its constitutionality. Those questions were expected to be the focus of much of Wednesday’s arguments.

Obama opposes law, House to defend

Led by President Barack Obama’s recent political about-face on same-sex marriage, which he now supports, his administration opposes the Defense of Marriage Act.

Traditionally, the solicitor general would defend the government’s interest in a Supreme Court case. However, Obama has already ordered the Justice Department to not take up the matter in court.

That prompted congressional Republicans, operating officially as the Bipartisan Legal Advisory Group of the House, to step in to lead the defense.

But there remains the question of whether any party could rightfully step in and defend the law after the Justice Department backed out. Besides the constitutional issue, the justices specifically ordered both sides to argue the supplemental question of whether the congressional group has “standing,” or legal authority to make the case.

Before Wednesday’s arguments, lawyers representing the House GOP said that they should be able to take the lead, since Windsor and the administration are taking the same legal position.

“Without the House’s participation,” said attorney Paul Clement, representing House leaders, “it is hard to see how there is any case or controversy here at all.”

Windsor’s legal team also said the House leaders could defend the law, at least partially, suggesting she wants resolution to the constitutional questions as soon as possible.

The momentous week for the Supreme Court to consider such a contentious issue kicked off on Tuesday with 80 minutes of arguments over California’s same-sex marriage ban.

The stakes in the two cases are high. The justices could, in one scenario, fundamentally alter how American law treats marriage. Polls show the public has become more aware of the issue and, in some cases, more supportive of allowing gays and lesbians to legally wed.

The California case

During Tuesday’s arguments, the justices seemed to lack consensus on both jurisdictional and constitutional questions of the voter-approved California law, known as Proposition 8, which bans same-sex marriage.

The overriding legal question in the California case is whether the Constitution’s guarantee of equal protection under the law prevents states from defining marriage.

The court could strike down laws across the country banning same-sex marriage, or it could leave the current patchwork of state laws in place, choosing to let state legislatures and state courts sort it all out.

“This was a deeply divided Supreme Court, and a court that seemed almost to be groping for an answer here,” CNN Senior Legal Analyst Jeffrey Toobin said after the arguments.

Four of the more liberal justices seemed at least open to the idea that same-sex marriage should be allowed in California. Three of the more conservative justices seemed aligned with the view that marriage should only be for a man and a woman, and it’s likely they’d be joined by Justice Clarence Thomas, who doesn’t speak at arguments.

That could leave Justice Anthony Kennedy as the swing vote, as has often been the case.

While admitting the law’s defenders are “not just any citizens,” Kennedy raised concerns about whether just 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.

A decision is not likely before June.

Nine states permit same-sex marriage

Andrew Pugno, general counsel for the Protect Marriage Coalition, the group defending Proposition 8, said its attorney had “credibly presented the winning case for marriage.”

“We think the hearing went very well,” he told reporters.

Attorneys representing the two couples seeking to overturn Proposition 8, meanwhile, 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.”

One of the plaintiff couples — Paul Katami and Jeff Zarrillo of Burbank, California, who want to marry but can’t because of Proposition 8 — contend the state is discriminating against them because of their sexuality.

“This is about our freedom and our liberty,” Katami said. “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.”

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.

Prohibitions seem to run counter to polls that show rising support overall for same-sex marriage.

A CNN/ORC International poll released on Monday found 53 percent of Americans now support same-sex marriage, up from 40 percent in 2007. As to how the federal government should handle the issue, another CNN/ORC International poll out Tuesday found 56 percent of the public feels the federal government should also legally recognize same-sex marriages.

CNN’s Tom Cohen and Shannon Travis contributed to this report.