New York’s legalization of same-sex marriage shows that the future belongs to marriage equality.

Here’s yet another sign of where things are heading. Over the past few years, Republicans have deployed increasingly libertarian arguments against President Obama’s policies. The New York Times’ behind the scenes account of the legislative battle over same-sex marriage in New York shows that the push for same-sex marriage appealed to Republican donors on those ideological grounds:

Would the donors win over the deciding Senate Republicans? It sounded improbable: top Republican moneymen helping a Democratic rival with one of his biggest legislative goals.

But the donors in the room — the billionaire Paul Singer, whose son is gay, joined by the hedge fund managers Cliff Asness and Daniel Loeb — had the influence and the money to insulate nervous senators from conservative backlash if they supported the marriage measure. And they were inclined to see the issue as one of personal freedom, consistent with their more libertarian views.

Within days, the wealthy Republicans sent back word: They were on board. Each of them cut six-figure checks to the lobbying campaign that eventually totaled more than $1 million.

It’s easy to overstate the Republican impact on the bill’s passage by spinning the results as coming from a “Republican controlled legislature.” Yes, four key votes for passage in the state senate came from Republican legislators — but the majority of the 33 votes came from Democrats. Nationally, Republicans remain supportive of a federal ban against same-sex marriage — bucking a growing national trend in support of marriage equality.

This is a losing fight for the Republican Party. Even though the Republican base is reluctant to accept the libertarian pitch on marriage equality, young people overwhelmingly support same-sex marriage rights, with Gallup finding that 70 percent of those 18-34 back it. Some of those young people are going to end up as conservative Republicans — but it’s likely that “conservative” is going to mean something different — at least as far as marriage equality is concerned.

What’s key here is we’re already seeing the kind of right-wing ideological arguments in favor of marriage equality gaining traction. Whether it’s a belief in federalism or individual rights, or simply the recognition that children are better off being raised by two parents — even two moms or two dads — folks on the right are eventually going to learn to accept, and even favor, the extension of same-sex marriage rights to gays and lesbians. There will come a time when the rhetoric of family values includes same-sex couples, when the pathetic pseudoscience of homophobia is seen as anachronistic and shameful as eugenics. New York, as the largest state to legalize same-sex marriage, is just the latest harbinger of what is to come.