CHICAGO (AP) — Legislation that ensures same-sex and interracial marriages are recognized as legal unions appears headed for final approval and President Joe Biden’s signature, a bipartisan agreement that reflects a wider acceptance of gay rights in both Congress and the country.

The measure, which would protect the rights of about a half million married couples, passed the Senate last week and heads to the House this week for near-certain approval.

For many of the couples whose marriages will be protected, approval of the Respect for Marriage Act brought a sense of relief and was cause for celebration. But they also say more work needs to be done.

The measure advanced due to supporters’ fears that a conservative majority on the U.S. Supreme Court may undo rights that took decades to obtain, just as the court overturned the longstanding right to abortion earlier this year. And it does not stop states from denying these couples the right to marry in the future, should the Supreme Court ever overturn the 2015 ruling legalizing same-sex marriage nationwide.

Still the broad support for the bill, which was backed by 12 GOP senators, was unexpected given the long and divisive history of the issue. Biden has said he will “promptly and proudly sign it into law.”

WHAT’S IN THE BILL?

The legislation says that federal and state governments must recognize legally celebrated marriages regardless of the individuals’ sex, race, ethnicity or national origin, and it would allow people to sue to enforce those rights.

It also maintains current religious freedom or conscience protections, stating that nonprofit religious organizations or nonprofits that are religious in nature do not need to provide goods, services or accommodations for the celebration of the marriages. For example, a church that doesn’t support same-sex marriage would not be required to rent out space for such a union.

HOW DID WE GET HERE?

It was roughly 25 years ago that a bipartisan majority passed the Defense of Marriage Act, or DOMA, which defined marriage as between one woman and one man. It said the federal government did not recognize same-sex marriages for purposes such as filing taxes or receiving Social Security survivor benefits, and that states didn’t have to recognize same-sex unions conducted in other states.

In 2013, the Supreme Court ruled that the part of DOMA that said the federal government wouldn’t recognize same-sex marriages was unconstitutional.

Two years later, in an opinion known as Obergefell v. Hodges, the court found bans on same-sex marriage unconstitutional. That monumental decision legalized gay marriage nationwide, ending bans in 14 states that still had them. Since then, hundreds of thousands of same-sex couples have married.

For interracial couples in the US, the right to marry has been recognized much longer. A 1960s-era Supreme Court decision, Loving v. Virginia, invalidated state laws that banned marriages between people of different races.

In the years after Obergefell, some supporters of gay rights worried the freedom to marry could one day be revoked, and pursued versions of the Respect for Marriage Act, said Jon Davidson, senior staff attorney for the ACLU’s LGBTQ & HIV Project and co-counsel on Obergefell.

But there wasn’t the urgency or political will to advance it — until this summer.

WHY NOW?

In June, a new conservative majority on the Supreme Court overturned Roe v. Wade, the 1973 decision that established the right to an abortion and had stood for almost 50 years. The ruling gave states the power to decide whether to ban abortion, and almost immediately a patchwork of laws went into effect, including near-total bans in about a dozen states.

Writing for the majority, Justice Samuel Alito said “(n)othing in this opinion should be understood to cast doubt on precedents that do not concern abortion.” But it was the words of a fellow conservative, Justice Clarence Thomas, that alarmed gay-rights supporters.

“I agree that ‘(n)othing in (the Court’s) opinion should be understood to cast doubt on precedents that do not concern abortion,’” Thomas wrote. “For that reason, in future cases, we should reconsider all of this Court’s substantive due process precedents.” That included Obergefell, Thomas wrote.

The statements “understandably terrified a lot of people” and gave new momentum to the Respect for Marriage Act, said Andrew Koppelman, John Paul Stevens professor of law at Northwestern University.

“We’ve got half a million same-sex couples in the United States, and Thomas essentially says to them, ‘I’m coming for you next,’” Koppelman said. “And so that generates some urgency that was not there before.”

There’s no case on the horizon that asks the Supreme Court to undo rulings that protect same-sex and interracial marriages. But Democrats opted to act while they had control of both chambers of Congress and the White House.

The House voted on an early version of the bill in July, and the final tally caught some by surprise: 267-157, with 47 Republicans voting in favor.

The vote reflected an overall change in the public’s views, Davidson said. At one point, most people in the U.S. opposed same-sex marriage. But in a June Gallup poll, 71% of U.S. adults said same-sex unions should be valid under the law.

Democrats delayed consideration of the bill in the 50-50 Senate until after the Nov. 8 election, hoping to get 10 Republicans on board and reach the 60-vote threshold necessary to overcome the filibuster.

Post-election, there was a new reason for Democrats to act quickly, for fear that a new GOP majority in the House would refuse to consider the bill come January.

WHAT WOULD THE BILL CHANGE?

“In many ways it freezes most of what is already the current law,” Davidson said, describing it as “a bulwark against the Supreme Court possibly reversing the Obergefell decision as it reversed Roe v. Wade.”

The legislation wouldn’t codify, or enshrine into law, Obergefell, which now requires states to issue same-sex marriage licenses. So if the bill is signed into law, and the Supreme Court later overturns Obergefell, some states could stop issuing those licenses. But all states would still have to recognize same-sex marriages performed legally in other states.

The practical effect of that would be that some people couldn’t get married in their own states, but all same-sex marriages would continue to be recognized and eligible for the legal benefits of marriage.

The bill also includes provisions to ensure federal benefits remain for same-sex married couples, such as tax, pension and health benefits.

WHAT HAS BEEN THE REACTION?

Most Republicans still oppose the legislation, saying it is unnecessary and citing concerns about religious liberty. In recent weeks some conservative groups also have spoken out against it. After the Senate approved the measure Tuesday, an official from Alliance Defending Freedom criticized it as jeopardizing the religious freedom of millions of Americans.

“This dangerously cynical and completely unnecessary bill is a direct attack on the First Amendment,” said Ryan Bangert, the organization’s senior vice president of strategic initiatives.

To Davidson, the vote shows how public perception on the issue has changed. He said the public has seen over the past few years that conservatives’ doomsday views of what could happen if same-sex couples were allowed was “fear-mongering.”

“They actually said ‘Civilization as we know it will end,’” he recalled. “And now same-sex couples have been able to get legally married and to have those marriages recognized in the United States for seven years everywhere in the country, and nothing bad has happened.”

At the same time, the LGBTQ community has been the target of violence, Davidson said, noting the recent murders at a gay nightclub in Colorado. He called on Congress to do more to protect the transgender community and others who have been victimized.

“Being able to have your marriage recognized and treated equally is important, but it’s not as important as being able to stay alive,” he said.