The passage of the Employment Non-Discrimination Act (Enda) in the US Senate yesterday, with the votes of 10 Republican senators, is not the decisive victory civil rights activists might hope for – the bill still faces a hard slog through the House. More practically, as Senator Elizabeth Warren (Democrat from Massachusetts) pointed out in a typically emphatic floor speech, this single political success does nothing for the thousands of homosexual and transgendered Americans who face employment discrimination today (surveys show that between 15% and 43% of the LGBT community experience some form).

But especially considering the voting records and public statements of those 10 GOP senators – most of them had explicitly opposed Enda at some point – it's impossible not to see the Enda vote as a watershed moment. Taken with Tuesday's election results, it points to another near-abandoned front of the once-lively culture war. Arizona Senator Jeff Flake, a surprise last-minute supporter of the bill, made news last spring when he admitted that it was probably "inevitable" that a GOP candidate will support same-sex marriage. And, he generously allowed, "I think he'll receive Republican support."

At the time – just six months ago – that seemed like an acknowledgment that the GOP base would grudgingly accept an outlier ("I think he'll receive Republican support"). The political atmosphere has begun to turn inside out; very soon, it will not be question of whether a GOP candidate could be a serious presidential contender and still support marriage equality, but whether a GOP candidate can be a serious presidential contender and not support marriage equality.

I take Senator Warren's reminder about the lived realities of LGBT individuals very seriously. Many thousands of them do not live with the openness and freedom that straight people take for granted. What's more, convincing Republican politicians to ban employment discrimination has proven to be something of an easier sell than marriage equality. Of the "Enda 10", only Mark Kirk, Rob Portman and Lisa Murkowski have taken a stand on the side of human decency. But advocating against the basic rights of LGBT Americans is becoming a political liability and not a strength. And, actually, Enda yes voter John McCain (who, along with yes vote Orrin Hatch, voted against the law in 1996) recently became a vocal proponent for LGBT rights internationally. In his strident op-ed response to Vladimir Putin, he criticized the Russian leader and his allies for "writ[ing] laws to codify bigotry against people whose sexual orientation they condemn".

Some of the movement toward gay rights on the right is admittedly of the "less bad" variety. Chris Christie's victory in New Jersey came even as some conservatives howled over his decision to drop a court contest over a judge's decision to allow same-sex marriage. A poll just this week in South Carolina showed that opposition to government recognition of same-sex marriage has dropped 26pt since the state passed a law against such unions in 2006 and 17pt since 2011. The law passed with 78% of the vote in 2006; in 2011 69% continued to agree with the position. Today, a bare majority, just 52%, agree … and, again, this is South Carolina, a state that Mitt Romney won by 10pts.

Pollsters have found that support for gay marriage trends alongside the number of respondents who say they know a gay person. Support for gay rights among politicians has contained some parallel growth, most dramatically with Rob Portman's decision to support marriage equality after his son came out as gay. (Murkowski also cited personal interactions with gay couples as a reason for her evolution on the issue.) Such one-to-one experiences are how social norms change at a fundamental level, but that kind of change takes time. If it were the only thing driving the GOP's shift, I'd be less optimistic than I am; the reason I think the timeline is far more accelerated than even movement in polls suggest is less about personal evolution than personal greed: politicians will adapt positions to conform to what donors want and more and more donors want conservatives candidates to endorse civil rights for gay people.

2012 saw the beginning of this. Last month, Republican "mega donor" Paul Singer poured millions into an advocacy group that's actually the second he's seeded to push the GOP toward the middle (over the last decade he's given $17m to the cause). Singer himself, whose son is gay, sees opposition to LGBT discrimination as a step toward full equality, including recognition of same-sex marriage. He also sees this position as fundamentally conservative, and, ironically, the language he uses in support of gay rights echoes that of unreconstructed culture warrior Ted Cruz's against the Affordable Care Act. He warns that a crack down on gay rights would come if "America engages in a terrible, terrible retreat from freedom, towards fascism, communism, whatever," Singer has said, "some totalitarian harsh state".

Opposition to ACA is actually an instructive point for Republicans resisting the momentum of gay rights. In Virginia, Ken Cuccinelli suffered for his association with backwards attitudes toward reproductive rights and personal privacy. That he appears to have profited from his early and vocal zeal to repeal Obamacare – or, at the very least, that this was less of a disastrous position for him than his anti-gay views – has rallied the right on that issue. Perhaps just as important, conservatives seem tickled that the tide of popular culture finally seems to be channeled into their side.

Personally, I believe the ACA will wind up working, and that history will validate it as an improvement over the tragic state of healthcare coverage prior to its passage. But as someone who believes in the value of a robust two-party system, I hope that the positive feedback loop that's heartened conservatives means a return to economic conservatism as its defining principle. I mean, I still think a lot of those conservative policies won't work, but to leave behind the ugliness and personal indignities of legislated inequality would mean immeasurable progress.

We're one of the few stable democracies in the world where the dominant conservative cohort rejects social moderates out of hand. Put another way, what do you call a fiscal conservative who wants to dismantle government involvement in national healthcare but who stays out of the gay marriage debate, the pro-life debate and rejects attempts to relax gun laws? The Prime Minister of Canada.

Canadian politics, at the moment, doesn't seem like the place to be picking role models. But one can hope for a future in which the response to an anti-equality Republican running for president elicits the response a Canadian might have: "What, are you on crack?"