It also flies in the face of an irrefutable trajectory of increasing support for same-sex marriage among Americans, especially younger ones. In a CNN/ORC International poll released Wednesday, a whopping 73 percent of respondents between the ages of 18 and 34 said they favored marriage equality. That’s the clear future of this issue, and Republicans are keenly aware that while the party’s formal opposition to abortion rights, for example, doesn’t contradict the prevailing sentiments of a majority of Americans or buck voter trends, opposition to same-sex marriage does.

Ken Mehlman, the former Republican National Committee chairman who came out as gay two years ago and has since pressed the case for marriage equality, told me, “A political party that ignores demography or ignores broader cultural trends does so at its own peril.”

But even apart from that, Mehlman, Singer and many other Republicans say that marriage equality, which in fact gets the government out of the business of controlling and casting judgment on people’s private lives, is consistent with conservative principles.

Singer said that it “very well fits within my framework of freedom,” adding that it promotes “family stability” and is a tribute to an institution in need of one.

“Obviously, the institution of marriage in America has utterly collapsed,” he said. That gay and lesbian couples nonetheless want to wed “is kind of a lovely thing and a cool thing and a wonderful thing,” he added.

The shifting Republican reality was underscored when 119 Republicans joined 92 Democrats in the New Hampshire House of Representatives three months ago in a vote to keep same-sex marriage legal in the state. Just three years ago, when it was legalized, only nine Republicans supported it.

In Massachusetts, Richard Tisei, a gay congressional candidate who supports marriage equality, was recently anointed one of the National Republican Congressional Committee’s “Young Guns,” signifying Republican leaders’ especially strong investment in his bid.

“I feel comfortable in the party,” he told me Friday.

Tisei is one type of candidate who might draw financial help from Singer’s super PAC, which, according to Singer, will soon have a budget “of a few million dollars,” factoring in expected support from collaborators and friends.

Singer said that more than a half-dozen Republicans who back same-sex marriage, who are contemplating it or who seem nudge-able have already attracted the super PAC’s attention.

I asked Chad H. Griffin, a progressive Democrat who heads the Human Rights Campaign, a leading advocacy group for gays and lesbians, what he made of Singer’s work on marriage equality.

“It’s absolutely necessary,” said Griffin. “We will never win marriage equality without bipartisan support.”

One Republican who unequivocally opposes marriage equality is the man Singer backs for president: Mitt Romney. Does that trouble Singer?

“I feel very strongly that Obama needs to be fired, and that the Republicans are right on most things,” he said, adding that with continued work on marriage equality, he expects to persuade more Republicans of its rightness, too.

“I think it would be naive of me to take this issue and just upend everything else I believe,” he said. “Because I think we’re making progress.”