Gay marriage is now legal in 37 states. Eighteen states have legalized it in the past six months alone. Meanwhile, public support continues to increase, with 61 percent of Americans saying they support gay marriage in a recent poll and just 35 percent opposed.

As gay marriage spreads across the country, in other words, Americans are becoming more accepting of it—and that could be a key factor as the Supreme Court takes up the issue in oral arguments on Tuesday. America, proponents argue, is now ready for gay marriage as never before.

As much as the many complicated legal questions before the Court, public opinion could be a crucial consideration as the justices contemplate a ruling that could legalize same-sex marriage nationally. Roe v. Wade is often cited as a decision that came before America was ready for it; Ruth Bader Ginsburg, for example, has said that while she believes in a woman’s right to have an abortion, the court went “too far, too fast” with Roe, and ended up damaging the abortion-rights movement as a result. The court is supposed to be above politics, but justices are leery of foisting sweeping social changes on the country.

Gay-marriage opponents now argue that legalizing gay marriage would provoke a similar backlash, unleashing a tide of anger at the court and galvanizing opposition to gay rights. But now that gay marriage is legal in so many states, that’s a harder argument to make, because the opposite has happened. Almost every state that has legalized gay marriage has seen it peacefully and uneventfully implemented. Even deeply culturally conservative states like Utah and West Virginia have now been allowing gay couples to marry for months, with little drama. There haven’t been mass protests in the streets; in fact, every state that has legalized gay marriage has seen a subsequent uptick in public support for it.

Sue Barton and her partner, Gay Phillips, who sued the state of Oklahoma to get it to recognize their California marriage, told me that the gradual change in  perceptions is noticeable even in Oklahoma. She attributed it to more people seeing firsthand that they have nothing to fear from gay people marrying. “The thing that I think has become more and more apparent is that we value marriage,” Barton said. “We want to support families in loving relationships.” Even many religious conservatives have become more accepting, as the gay marriages around them force them to confront that fact, she said.

According to last week’s Washington Post/ABC News nationwide poll, gay marriage is supported by 64 percent of people in states where it is legal, and 54 percent in states where it is not. Even many who don’t support gay marriage seem to have accepted it: Nearly three-quarters of Americans consider the legalization of gay marriage inevitable.

The remarkable lack of resistance to the spread of gay marriage is itself a new development. When a Hawaii court said gay marriage was permitted by the state’s constitution in 1993, legislators rushed to amend the constitution to forbid it, and within a few years Congress had responded with the Defense of Marriage Act. In 2004, when Massachusetts became the first state to issue marriage licenses to same-sex couples, there were protests in the streets. If that were the kind of public reception the Supreme Court could anticipate, the justices might well be reluctant to wade into such a divisive issue.

But times have clearly changed, thanks in part to a sophisticated public-persuasion campaign by gay-marriage advocates. “We have worked very hard to build a critical mass of public support, a nationwide majority for marriage, to show the justices that America is ready for the freedom to marry,” says Evan Wolfson, the president of Freedom to Marry, the group that has spearheaded the political strategy. “The justices can do the right thing knowing not only that history will vindicate them, but that the public is ready.”

There is one high-profile exception to the smooth and rapid adoption of gay marriage in recent months: Alabama, where the state supreme court, led by Chief Justice Roy Moore, has defied a federal court’s attempt to unwind the state’s gay-marriage prohibitions. In this, it has been aided by a quirk of state law that puts the issuing of marriage licenses under the purview of the judiciary. Advocates say that’s the exception that proves the rule, but they’re also bracing for more such resistance if the Supreme Court nationalizes gay marriage, as most court watchers expect, when it rules later this year.

Lawmakers in other states have sought to pass broad new “religious liberty” bills that opponents call a license to discriminate. But recent controversies over such legislation in Indiana and Arkansas resulted in the bills being watered down. Some Republican presidential candidates are still rushing to reassure the all-important Iowa caucus electorate that they’re strongly opposed to gay marriage. But most of them seem to want to avoid talking about the issue—as Mitt Romney largely did in 2012.

Gay-marriage advocates believe the situation facing the Court now is less like Roe and more like Loving v. Virginia. That’s the case in which the Supreme Court legalized interracial marriage in 1967—by which time it was already legal in 34 states. The Loving ruling was widely accepted even though, at the time, 70 percent of Americans opposed interracial marriage. By that measure, the country is far more ready for gay marriage now than it was for interracial marriage in the late 1960s.

The more  gay people Americans see getting married, the less alarmed the prospect seems to make them. Gay marriage hasn’t accelerated the decline of heterosexual marriage, according to social scientists, much less caused social collapse. As gay people have become more visible and accepted members of American society in recent decades, their relationships and families are increasingly seen as worthy of recognition.

“The tide of public opinion, even in Alabama, is shifting,” Paul Hard, a professor in Montgomery who sued to get himself listed on the death certificate after his husband died in a car accident, told me. “My friend’s very conservative father said the other day, ‘I don’t support the way he lives, but nobody should go through what he went through.’ A lot of people are starting to reexamine how they are treating their brothers and sisters and neighbors and coworkers.”

For a Supreme Court that doesn’t like to make too many waves, that might be the most persuasive argument of all.