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.”