Updated 5:06 p.m. | It would have been unthinkable, maybe only a year ago, that legislation to expand gay civil rights would win more bipartisan support than legislation protecting college kids from a doubling of their student loan rates.

That’s what happened in the Senate this week. Tuesday morning, three Republicans joined all 12 Democrats on the Health, Education, Labor and Pensions Committee in voting for a federal prohibition on workplace harassment and job discrimination based on sexual orientation or gender identity. 

Then, at lunchtime, a White House-backed proposal to keep the Stafford loan rate at 3.4 percent for another year was blocked on the floor after no Republicans lined up behind it.

The two roll calls underscore one of Washington’s most unexpected but important storylines of the year: the progress of people who aren’t heterosexual in overcoming the walls of government-countenanced discrimination.  Congress now shares a starring role with the Supreme Court as the most important venue for their cause, with President Barack Obama squarely on board.

White House Press Secretary Jay Carney said the president was eager to sign the job bias prohibition because it “upholds America’s core values of fairness and equality.”

The HELP Committee’s 15-7 tally guarantees a majority of senators would vote for passage, and that support is at most a handful shy of the 60 senators necessary to overcome a filibuster by Republican cultural conservatives.

Advocates say those votes are within reach and that Majority Leader Harry Reid was prepared to put the bill on the floor as soon as passage is assured.

Doing so by early fall would allow a full year for lobbying the House, where passage at the moment looks to be a decided long shot. Speaker John A. Boehner has made clear that such consequential bills will advance only if they have proven support from a majority of his GOP majority.

The companion bill to what advanced in the Senate on Tuesday has just three GOP sponsors. Nine other Republicans voted “yes” when the House passed a somewhat narrower measure; it would have banned job discrimination based on sexual orientation but was silent on gender identity.

Still, public sentiment in favor of gay rights is expanding so rapidly that the political dynamic could be different by next summer. It’s not totally implausible that, even before the next election, advocates of gay rights may achieve their top legislative goal for the past two decades — something that’s arguably as important as the twin victories won at the high court two weeks ago.

“I think society is there and the things that have happened in the Supreme Court show we’re ready to move on in a way we haven’t moved on in the past,” said HELP Chairman Tom Harkin of Iowa, who has made enacting the anti-discrimination bill the top priority of his term before retiring next year.

The national discussion created by the California ban and Defense of Marriage Act cases helped prompt at least eight senators to reverse course and declare their support for gay marriage, creating a majority of 54 on that side of the debate now. The recent converts include Lisa Murkowski of Alaska and Mark S. Kirk of Illinois, who were joined by Orrin G. Hatch of Utah as the Republicans voting “yes” in committee.

The bill has one other GOP sponsor, Susan Collins of Maine, who’s not on the committee. Those four Republican votes, combined with those of the 51 Democratic co-sponsors, would bring the floor majority for the bill to 55.

Bill Nelson of Florida, who was among those who switched to support gay marriage this spring, is among the three Democrats who have not signed on. The others are Mark Pryor of Arkansas and Joe Manchin III of West Virginia, who are opposed to gay marriage (so is Democrat Mary L. Landrieu of Louisiana, but she’s a bill co-sponsor).

Lobbyists for the bill say they hope to reverse the current opposition of two Republicans: Richard M. Burr of North Carolina, who was among the eight GOP senators who voted to repeal the “don’t ask, don’t tell” law three years ago; and Rob Portman of Ohio, who has declared himself a supporter of gay marriage. They also hope to woo Jeff Flake of Arizona, who voted in the House for the 2007 version of the bill. That measure would not have extended to transgender workers, which the Senate bill does.

That legislation would prohibit businesses of 15 or more workers, as well as employment agencies and labor organizations, from discriminating on the basis of sexual orientation or gender identity when making hiring, firing, payment or promotion decisions. In a concession essential to winning any GOP votes, the bill has an exemption permitting churches and other religious organizations to make personnel decisions based on their faith tenets.

By the start of next month, same-sex marriages will be legal in 13 states and Washington, D.C.  But 17 states and D.C. prohibit workplace discrimination based on either sexual orientation or gender identity — as do a majority of Fortune 500 companies.

The tide of national sentiment may once again drag Congress to the political place it needs to be.