New York became the largest-population state in the country to legalize gay marriage on June 24 when its Republican-controlled Senate passed the Marriage Equality Act, a move that surprised many.

But for those on the inside, it was not a shock, just the culmination of months of hard work and another step in what they see as an evolution in Republican attitudes toward gay marriage.

Pressure to pass the bill had been building, not only from grassroots organizations but also from the top political figures in Republican circles. Dick Cheney and Barbara Bush, George W. Bush’s daughter, both came out publicly in support of the bill. Behind the scenes, Republican donors and lobbyist were working months in advance to gather key votes in the New York state legislature.

“It wasn’t surprising to us,” said R. Clarke Cooper, executive director of the Log Cabin Republicans. “This just didn’t happen by accident. There was a very precise lobbying effort. We had all our chapters working on it, as well as allies like [New York City Mayor Mike] Bloomberg and Ken Mehlman putting sweat into this.”

Among the other behind-the-scenes forces were top-tier Republican donors like Paul E. Singer, chairman of the conservative Manhattan Institute, and Steven A. Cohen, a hedge fund manager at SAC Capital Advisors. According to the New York Times, Singer donated $425,000 of his own money and personally solicited an additional $500,000 in donations. He also hosted private meetings to make the case for legalizing gay weddings in New York to other conservatives.

Mehlman, the former chairman of the Republican National Committee who came out as gay last year, said New York’s legalization of gay marriage was part of a larger shift among both Republicans and the public at large. (Obama almost approves of same-sex marriage)

“What is most significant is how public opinion is moving on this issue,” Mehlman said in an interview with BigThink. “Part of this movement involves increasing numbers of Republicans and conservatives who recognize it is consistent with core Republican and conservative values such as maximizing freedom, strengthening families and promoting family values and following the Golden Rule.”

And as more Republicans have dropped opposition to gay marriage as a talking point, their numbers among gay voters have increased. In 2010 — an election cycle dominated by the economy, rather than social issues — Republicans picked up 31 percent of the gay vote. That’s an uptick from 23 percent in 2004.

“The party took notice of that,” said Christian Berle, deputy executive director of the Log Cabin Republicans. “Candidates are recognizing that creating a big tent will make you more attractive to more voters.” (Equal Rights Amendment seen as back door to same-sex marriage)

But while Republicans running for Congress have tended to shy away from social issues in recent years, there has not been a similar shift among Republicans on the national stage. Many GOP presidential candidates gave deference to states’ rights when speaking about New York, but almost all said they support a constitutional amendment banning gay marriage at the federal level.

“In New York state, they have passed the law at the state legislative level and, under the 10th amendment, the states have the right to set the laws that they want to set,” Congresswoman Michele Bachmann, Minnesota Republican, said.

Bachmann later said, however, she would push for a constitutional amendment banning gay marriage if she were elected.

Former Speaker of the House Newt Gingrich took a similar tack, saying the legislature was “the right venue” for the decision, rather than the courts, but that the country was “drifting towards a terrible muddle” on the issue.

“I believe that marriage is between a man and a woman,” Gingrich said. “I think that’s what marriage ought to be and I would like to find ways to defend that view as legitimately and effectively as possible.”

Former Massachusetts Gov. Mitt Romney opposes same-sex marriage and civil unions, but he has said that people in nontraditional relationships should have hospital visitation and other rights. Former Minnesota Gov. Tim Pawlenty also believes marriage is defined as between a man and a woman.

The most vocal candidate against gay marriage, both historically and currently, is Senator Rick Santorum (R-Pennsylvania), whose frothy rhetoric against gay marriage has earned him the ire of many gay groups.

GOP presidential contender and former Godfather’s Pizza CEO Herman Cain said he believes homosexuality is a sin but wouldn’t object to hiring gays or lesbians in his administration if elected. (Juan Williams warns Obama gay marriage push upsets black community)

Rep. Ron Paul, Texas Republican, has said he personally does not support same-sex marriage, but he favored repeal of the military’s “don’t ask, don’t tell” rule and does not believe the federal government should be involved in marriage at all.

On his Web site, former New Mexico Gov. Gary Johnson says he “does support gay and civil unions. However, he does not support gay marriage.”

The rhetoric shows a Republican Party still caught somewhere between libertarianism and social conservatism, federalism and fundamentalism. Cooper said that, at the very least, the New York vote will force GOP presidential candidates to sharpen their positions.

“It’s June 2011, so a lot can happen between now and summer 2012,” Cooper said. “But I think [gay marriage] is going to be a discussion point. This is going to force campaigns to do research, dialogue and get educated on the issue. We’re going to see the candidate’s positions get fleshed out.”