LAS VEGAS >> As bans against gay marriage crumble and public opinion on the issue shifts rapidly, some Republicans are pushing the party to drop its opposition to same-sex unions, part of a broader campaign to get the GOP to appeal to younger voters by de-emphasizing social issues.

This month, the Nevada Republican party dropped statements on marriage from its party platform, making it the second state party in the nation to do so after Indiana’s GOP quietly jettisoned its plank in 2012. A gay-rights group last week launched a $1 million campaign to get the national party to remove from its platform a definition of marriage as between a man and a woman, while a group of major Republican donors is pushing for the GOP to become more supportive of gay rights across the board.

“There are people with sincerely held beliefs on both sides of the marriage issue, and that seems to be where the party is heading,” said Jeff Cook-McCormac, an adviser to the American Unity Fund, which has been financed by wealthy donors such as hedge-fund billionaire Paul Singer to push the GOP to back gay rights. “The Republican Party in Nevada is doing something that I think we’re going to see a lot more of, which is appealing to the things that unite Republican voters across the country — bread and butter issues.”

But social conservatives warn that if the GOP abandons its core moral principles, it may also lose loyal voters.

“It is very much a mistake for the GOP to step away from marriage. The rank-and-file Republicans, mainstream Republicans, very much believe marriage is between a man and a woman,” said Chris Plante, spokesman for the National Organization for Marriage. “For the GOP to give in to elites, to promises of money, and to progressives within the party is the wrong thing. It’s bad politics. Marriage is a winning issue.”

The greatest test will come in Nevada, a swing state where the state party also dropped its opposition to abortion during its biannual convention on April 12. The push arose from Clark County, home to libertine Las Vegas and three-quarters of the state’s population.

“Younger people believe they’re getting screwed by the Democrats on fiscal issues, and screwed by Republicans on social issues,” said Nick Phillips, the Clark County party’s political director. “Take that away, and you’ve got a party you can get behind.”

The state has no organized bloc of socially conservative voters. The state’s Republican governor, Brian Sandoval, supports abortion rights, recently decided to drop the state’s defense of a lawsuit challenging its gay-marriage ban, and is so popular that no significant Democrat is challenging him for re-election this year. But there is still some bitterness over the platform within the party, which has been riven for years by infighting among rival conservative factions.

“If they come up with a totally neutered, watered-down platform that stands for nothing, they’re going to disgust the base,” said Ira Hansen, a Republican Nevada assemblyman. “They alienate them and humiliate them and then expect them to vote.”

Seventeen states allow gay marriage and 59 percent of Americans supported it in a recent Washington Post-ABC News poll. That’s a sharp turnaround from a decade ago, when same-sex marriage was a Republican wedge issue that galvanized social conservatives and was widely unpopular with voters. Although a majority of Republicans remain opposed to gay marriage, the dynamic is reversed among younger members of the GOP. A Pew Research Poll found 61 percent of Republicans ages 18 to 29 supported gay marriage.

Even before Nevada’s vote, activists in other local Republican parties were trying to shed the gay-marriage issue. Oregon Republican activists at an annual conference last month endorsed a ballot measure to legalize gay marriage in that state, though social conservatives boycotted the event. In liberal Marin County, Calif., where Democrats outnumber Republicans 3-1, the county party issued a statement last summer saying it supported legalizing gay marriage.

“No one really knows where you stand on something until you tell them,” said Kevin Krick, chair of the Marin County Republican Central Committee.

Still, pushes to change course on same-sex marriage have provoked staunch resistance. In Broward County, Fla., a Republican party secretary who tried to rally support for pro-gay-marriage Republicans last summer faced fierce internal backlash and has since left the post. In Illinois, then-Republican party chairman Pat Brady took heat last spring when he made statements supporting gay marriage, and he stepped down to become a lobbyist. In party elections last week, however, six of the seven committeemen who had called for Brady’s ouster were themselves replaced.

One of the main national gay-rights groups, Freedom to Marry, argues that Republicans now are like Democrats a decade ago — they want to support gay marriage but are afraid of possible political repercussions.

Freedom to Marry is helping fund a campaign to change that by urging delegates to remove opposition to same-sex marriage from the party’s national platform. Campaign manager Tyler Deaton said the goal is simply to remove the language opposing gay marriage rather than replace it with an endorsement of a union that remains opposed by some members of the GOP.

“Our aim is to make the national platform less divisive toward gay people and their families — and more focused on unifying all conservatives around our core beliefs,” Deaton said.

Republican National Committee spokeswoman Kirsten Kukowski said the party platform “stands for traditional marriage” and potential changes won’t come up until the next national convention in 2016.

Mark McKinnon, a former adviser to President George W. Bush, said that even if Republicans are balking at publicly accepting gay marriage, they are clearly walking away from the issue.

“The heat is off, the wedge has lost its edge,” said McKinnon, who is helping Freedom to Marry promote same-sex union support in the South. “Republican candidates this cycle may not be running on the issue of gay marriage, but they’re not running against it.”

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AP reporter Nicholas Riccardi contributed from Denver.