Matt Slocum, AP
In this June 26, 2013, file photo, Sean Lewrence, of Philadelphia, holds up a flag during a rally for gay marriage, on Independence Mall in Philadelphia. A federal appeals court on Thursday, Nov. 6. 2014, upheld anti-gay marriage laws in four states, breaking ranks with other courts that have considered the issue and setting up the prospect of Supreme Court review. (AP Photo/Matt Slocum, File)

Ten years after Massachusetts became the first state to allow same-sex marriage, gay and lesbian Americans can be wed in 35 states and the District of Columbia (Florida will boost that number to 36, starting Tuesday). This year, the Supreme Court may put an end to the skirmish by legalizing what progressives call “equality” and conservatives dub a “redefinition” of this cherished social institution.

The court last ruled on gay marriage in 2013 when the justices gutted much of the federal Defense of Marriage Act in United States v. Windsor and delivered a massive blow to anti-gay marriage advocates. Since then, the court has acted by not acting — in effect, doubling the number of states where gay marriage is legal, from 17 to 35, by refusing to hear a slew of appeals last year.

In November, the Cincinnati-based 6th U.S. Circuit Court of Appeals upheld gay marriage bans in four states, which will almost certainly require the high court to decide the issue once and for all.

Conservative Christians have been among the most ardent opponents of gay marriage and rights for decades. How will they respond if the Supreme Court makes gay marriage legal nationwide?

The answer, it turns out, depends on which Christian you’re speaking to.

Russell Moore, president of the Ethics and Religious Liberty Commission of the Southern Baptist Convention, has become a leading face for the next generation of Christians opposed to gay marriage. He expects the court to take up marriage this year, and is not optimistic about how they’ll rule given the Windsor decision.

Even so, he doesn’t think such a ruling will make a whit of difference for most of his fellow evangelicals.

“Evangelicals are, by definition, defined around the Bible and the gospel,” Moore said. “The Scriptures are clear on what marriage is, and clear on the sin of sexual expression outside of the marriage covenant of a man and woman.”

If the court were to “redefine marriage,” Moore said Christians should “be ready to offer an alternative vision of marriage and family” that doesn’t include same-sex unions. Interestingly, his vision would be promoted primarily within the church rather than changing laws through political action.

“We must articulate these truths about marriage in our gospel witness, and we must embody these truths in churches that take marriage seriously,” Moore said. “This means we must start teaching our children a countercultural word about what it means to be men and women, about what marriage is, and that must begin not in premarital counseling but in children’s Sunday school.”

He contends that anyone who supports gay marriage is not an evangelical.

Ryan Anderson, a fellow at the Heritage Foundation who co-authored “What is Marriage?” with Princeton scholar Robert P. George, is a powerful voice among young conservatives. Anderson thinks the court is “very likely” to take up same-sex marriage in 2015 given the 6th Circuit decision, and he believes the decision will come down to Justice Anthony Kennedy, who has authored the court’s most significant gay rights decisions.

Anderson (a Roman Catholic, like Kennedy) said the majority of evangelicals will remain opposed to gay marriage regardless of the ruling. But he believes the law can serve a “pedagogical function,” so legalizing gay marriage could “change the public understanding of behavior.” While Anderson won’t predict how conservative Christians at large would react, he said much depends on the behavior of LGBT advocates.

“We’ll have to see how gracious or vindictive voices within the LGBT community are in their responses,” Anderson said. “Will they become a live-and-let-live movement or a stamp-out-dissent movement? If there’s respect, there’s likely to be less pushback from conservatives.”

Anderson and Moore represent a sizable chunk of the Christian population — a majority of evangelicals and half of practicing Catholics oppose gay marriage — but they are not all of it. In recent years, many Christians, particularly younger Christians, have changed their minds on the matter. From 2003 to 2013, support for gay marriage among white evangelicals more than doubled, and support among Catholics rose by 22 percentage points.

Brandan Robertson, national spokesman for the group Evangelicals for Marriage Equality, an organization that believes “you can be a devout, Bible-believing evangelical and support the right of same-sex couples to be recognized by the government as married,” also believes the court will take up the issue this year.

“Christians are increasingly saying that they need to stand up for LGBT equality no matter what they believe theologically,” he said, “and they are doing this not because they are American, but because they are followers of Christ.”

Though Robertson is strident in his support of “marriage equality,” he shies away from addressing whether homosexual behavior is moral, or sinful — representing many Christians who draw a distinction between civil marriage and Christian marriage.

Justin Lee, executive director of the Gay Christian Network and author of “Torn: Rescuing the Gospel from the Gays-vs.-Christians Debate,” believes a Supreme Court decision in favor of gay marriage is inevitable. While his organization seeks to welcome Christians from a range of perspectives, his comments about marriage mirror Robertson’s.

“There is a distinction between Christian marriage in the eyes of God and civil marriage in the eyes of the state,” Lee said. “My hope is that Christians will continue to see that what the state says marriage is may not line up with what the church or God says.”

Conservatives are changing their minds, albeit slowly, about homosexuality, but are shifting more rapidly on gay marriage.

Even though about half of conservative Christians now believe that gay marriage is inevitable, don’t expect them to slip quietly into the night. Progressives may have the momentum, but conservatives still have a majority. Look to evangelicals to shore up the theology around holy matrimony, and fight to defend their religious liberty rights to oppose same-sex marriage.

“A Supreme Court ruling might be the last word in legal terms,” Moore said, “but it is hardly the last word in cultural or spiritual terms.”