WASHINGTON (CNN) – A majority of justices raised questions in oral arguments Wednesday about the federal Defense of Marriage Act, indicating the Supreme Court may strike down a key part of the law that denies legally married same-sex couples the same benefits provided to heterosexual spouses.

A ruling is expected within three months on the constitutionality of the 1996 law that defines marriage for federal purposes as only between one man and one woman.

Wednesday’s arguments concluded two days of 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.

Afterward, Edith “Edie” Windsor, 83, stood on the steps of the courthouse — near the “Equal Justice Under Law” slogan engraved above — and proclaimed something she hid for decades before her challenge against the act known as DOMA.

“I am today an out lesbian, OK, who just sued the United States of America, which is kind of overwhelming for me,” she said. She had just watched almost two hours of oral arguments before the nation’s highest court on how she had to pay higher estate taxes than someone in a heterosexual marriage.

Windsor tried to explain to reporters why she and her late spouse, Thea Spyer, married in New York when the law allowed it after decades together.

Marriage, she said, is “a magic word, for anyone who doesn’t understand why we want it and why we need it.”

“We did win in the lower court,” Windsor added, then later predicted: “I think it’s gonna be good.”

Under DOMA, Social Security, pension and bankruptcy benefits, along with family medical leave protections and other federal provisions, do not apply to gay and lesbian couples legally married in states that recognize such unions.

Windsor was forced to assume an estate tax bill much larger than heterosexual married couples 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.

“What kind of marriage is that?”

The court appeared divided along ideological lines during the arguments about whether DOMA is discriminatory and steps on state marriage laws for gays and lesbians.

If legally married homosexuals were being denied more than 1,100 federal benefits, “what kind of marriage is that?” asked Justice Ruth Bader Ginsburg, who said the discriminatory effect is “pervasive.”

“What gives the federal government the right to define marriage?” asked Justice Sonia Sotomayor.

The potential swing vote, Justice Anthony Kennedy, also questioned the reach of DOMA, saying it presents a “real risk of running into traditional state police power to regulate marriage.”

Kennedy’s point caused court observers to speculate he would join the four normally liberal-leaning justices to create a majority against the act.

On the other side, Chief Justice John Roberts repeatedly asked whether it would step on state power to do the opposite of DOMA — pass a law providing full federal benefits to any legally married same-sex couple.

When Windsor’s lawyer argued in court there was a “sea change” afoot today in support of same-sex marriage that leaves DOMA outdated, Roberts said that is because of “the political effectiveness of those on your side” swaying public opinion.

Roberts and Justice Antonin Scalia also suggested DOMA could still remain in place as a valid extension of congressional authority, as 41 states do not allow same-sex marriage.

Paul Clement, the high-profile lawyer hired by House Speaker John Boehner and fellow Republican legislators to defend DOMA, suggested the act was passed as a “cautious approach” in response to initial efforts in some states to change state marriage laws to include homosexuals.

“In 1996 something was happening” in the country, Clement said, adding that Congress wanted to created uniformity in the federal sphere and not sow confusion in states that did not want same-sex marriage.

However, Justice Elena Kagan drew an audible gasp from the packed courtroom by quoting from the official House reports of 17 years ago, when legislators stated one reason to pass DOMA was to “express moral disapproval” over gays and lesbians being allowed to wed.

It was not until 2004 that Massachusetts became the first state to legalize same-sex marriage.

No consensus was reached from the bench on the gateway or jurisdictional questions — whether House Republicans were on solid legal footing when they stepped in and defended the law after President Barack Obama and his Justice Department reversed their position by concluding DOMA was unconstitutional.

The administration changed its mind after initially defending the law before a federal judge hearing the Windsor lawsuit.

Roberts tweaked Obama for not having “the courage of conviction” to continue enforcing the law even if he thought it was discriminatory.

At a news conference later Wednesday, House Democratic leader Nancy Pelosi of California called congressional Republicans irresponsible for funding the defense of what she called a discriminatory law at a cost she put at $3 million.

“On the basis of what I heard, the questions of the justices, the response of the participants, I’m very optimistic that DOMA will be struck down,” Pelosi said.

“We didn’t have horns”

To Windsor, Wednesday’s arguments represented another step in the evolving history of gay rights in America.

For years, she said, she wore a circle of diamonds as a pin instead of a traditional diamond ring to hide her lesbian relationship from co-workers.

“We all lived, really, behind masks and in closets, indeed,” Windsor explained. “So what happened is there was, as we increasingly came out, people saw that we didn’t have horns. People learned that, okay, we were their kids and their cousins and their friends, all of whom were coming out for the first time. And I think it just, it just grew to where we were human beings like everybody else. And I really think that’s what made the change.”

Laughing, she told reporters: “I’m talking to you freely. I’d have been hiding in a closet 10 years ago.”

Public interest remained high outside the court in advance of Wednesday’s session, 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 DOMA.

“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.”

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

The California case

During Tuesday’s arguments, the justices seemed to lack consensus on both jurisdictional and constitutional questions relating to 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 refusing marriage to a defined class of people.

When it rules, 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 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.

Nine states permit same-sex marriage

Among the 41 states that now forbid same-sex marriage, 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% of Americans now support same-sex marriage, up from 40% in 2007. As to how the federal government should handle the issue, another CNN/ORC International poll out Tuesday found 56% of the public feels the federal government should also legally recognize same-sex marriages.

The fate of one of the nation’s most divisive issues was now in the hands of the U.S. Supreme Court.

The nine justices will decide whether Proposition 8 — which amended the state Constitution to define marriage as between a man and a woman — will stand as law in California.

Carolyn Costello has local reaction.

WASHINGTON (CNN) — After years of struggle on both sides of the issue, the question of same-sex marriage goes before the U.S. Supreme Court this week.

People were already lining up outside the court Friday morning for the limited number of seats available Tuesday and Wednesday, when the justices will hear oral arguments on two cases.

For those of you who won’t be in the courtroom, here’s a look at what to expect.

As Joe Biden might say, it’s a big family deal

These are no ordinary laws before the Supreme Court: They represent battles over a generations-old concept of marriage and the rights of an increasing number of families in legally recognized gay and lesbian relationships.

There are an estimated 120,000 legally married same-sex couples in the United States.

Nine states and the District of Columbia now allow same-sex couples to marry, and a dozen others recognize “civil unions” or “domestic partnerships” that grant some of the same benefits without full marriage rights.

But 29 states have added bans on same-sex marriage to their constitutions, including California, the most populous state.

Supporters of the same-sex marriage ban in California argue that it’s not just tradition but also biology: “The two sexes are different to the core, and each is necessary — culturally and biologically — for the optimal development of a human being,” Rutgers University sociologist David Popenoe has written.

How we got here

It starts back in 1993, when Hawaii’s Supreme Court found that the state couldn’t deny same-sex couples the right to marry without a “compelling reason” and sent the issue back to the state legislature.

Hawaii lawmakers quickly passed a law banning gay marriage, and advocates of traditional marriage began mobilizing to fight the prospect of gays and lesbians being able to marry.

That led to the passage of the federal Defense of Marriage Act, the 1996 legislation that forbids the recognition of same-sex marriages nationwide and bars married gay and lesbian couples from receiving federal benefits.

But DOMA is becoming an orphan. Two federal appeals courts have already struck down its benefits provision; the Obama administration has refused to defend it; and former President Bill Clinton, who signed it, now calls it “incompatible with our Constitution.”

With the Justice Department now arguing against it, Republicans in the House of Representatives hired their own lawyers to defend the act.

The California ban, known as Proposition 8, passed by a 52-48% margin in 2008.

It eliminated the right to marry that had been recognized by California courts earlier that year.

Opponents of the measure challenged it in court and have succeeded in convincing federal judges at the district and appellate levels to find the ban unconstitutional.

The justices will hear oral arguments on Proposition 8 on Tuesday. On Wednesday, they will take up DOMA.

A civil right, or a political question

One the biggest issues facing the justices is whether they can — or should — issue a ruling that will effectively broaden the legal definition of marriage, long restricted to heterosexual couples.

Backers of DOMA and Proposition 8 say it should be up to the public to make that decision, not the courts.

“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 told CNN’s State of the Union.

“We need to leave this debate to the democratic process, which is working.”

But 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.”

“It is one thing to read the polls, which we have discussed, which show again that a majority of Americans are in favor of same-sex marriage,” Harris said. “But it is more important to read the Constitution.”

Who to watch

Same-sex marriage advocates will be watching Justice Anthony Kennedy during this week’s arguments.

The generally conservative Reagan appointee has authored two opinions that advanced gay rights during his tenure, striking down state laws criminalizing homosexual sodomy and striking down a Colorado constitutional amendment that forbade local gay-rights ordinances.

In that 1996 case, Kennedy wrote for the court, a state can’t decide that a class of people are “a stranger to its laws.”

Conservative supporters of the bans have turned their eyes toward Justice Ruth Bader Ginsburg.

The justice, a Clinton appointee, told a Columbia University forum in 2012 that the 1973 Roe v. Wade decision that struck down state bans on abortion short-circuited a political consensus on abortion rights.

Karl Rove, the onetime strategist for former President George W. Bush, told ABC’s “This Week” on Sunday that Ginsburg may oppose a sweeping decision in support of same-sex marriage.

“What we may see is a decision here that in essence is not a 5-4 decision, but a 6-3, 7-2 that says ‘leave it up to the states,’” said Rove, whose old boss once endorsed an amendment to the U.S. Constitution to ban same-sex marriages. “In fact, we could see an 8-1.”

CNN legal analyst Jeffrey Toobin, the author of a lengthy Ginsburg profile for The New Yorker, said Ginsburg is likely to find the Defense of Marriage Act unconstitutional but isn’t likely to knock down bans on same-sex marriage nationwide.

“She does not believe in grand pronouncements, even liberal grand pronouncements, from the Supreme Court,” Toobin said.

A shifting landscape

The court is hearing arguments as a public shift toward same-sex marriage appears to be gathering speed.

The proportion of Americans who support same-sex marriage has grown from around 40% in 2007 to 53% in a CNN/ORC International poll conducted last week; 44% remain opposed.

Barack Obama ran for president in 2008 as a supporter of civil unions but not same-sex marriage. In 2012, months before facing voters again, he said his thinking had shifted and that he supported marriage rights for gays and lesbians.

“I had hesitated on gay marriage, in part, because I thought civil unions would be sufficient,” he said.

“I was sensitive to the fact that — for a lot of people — that the word marriage is something that provokes very powerful traditions and religious beliefs.”

Obama’s Republican challenger, Mitt Romney, ran as a defender of traditional marriage, and the party’s platform opposed same-sex marriages.

But since November, numerous GOP figures have emerged as supporters of same-sex unions.

Dozens of high-profile Republicans — including former party Chairman Ken Mehlman, ex-presidential hopeful Jon Huntsman and actor Clint Eastwood — filed a friend-of-the-court brief arguing that Proposition 8 should be struck down.

And earlier this month, Sen. Rob Portman of Ohio announced he is now a supporter of the freedom to marry after finding out that his son — a Yale sophomore — is gay.

“Eventually, as time marches on, this is a country that believes pretty squarely in marriage equality,” former Bush spokeswoman Nicolle Wallace told “Fox News Sunday.”

DOWNTOWN LOS ANGELES — Advocates of gay marriage held a candlelight vigil Sunday night ahead of U.S. Supreme Court hearings on the issue this week.

Dozens of supports gathered at the L.A. City Hall West Steps on Temple and Spring Streets.

Some who spoke included lesbian and gay families who could be impacted by the court’s ruling on both Prop. 8 and DOMA, as well as elected officials, faith leaders, community activists and celebrities.

The event was organized by Founders of the Metropolitan Community Church of Los Angeles, California Faith for Equality, Family Equality Council, GetEQUAL, GLAAD, Good As You, Human Rights Campaign, Marriage Equality USA, National Gay and Lesbian Task Force and the New Organizing Institute.

Thousands are expected to rally in Washington, D.C. in front of the U.S. Supreme Court on Tuesday when the court takes up Prop. 8.

Christina Pascucci reports.

The Supreme Court announced Friday it will rule for the first time on same-sex marriage by deciding the constitutionality of California s Proposition 8.

The Supreme Court is in the process of deciding what cases it will rule on in the next year.