In France, lawmakers have now voted to legalize gay marriage, after months of debate and street protests. Here in the United States, lawmakers may be poised to act in another arena where the battle over gay civil rights is being fought: The workplace.

Senator Jeff Merkley, one of the lead sponsors of the Employment Non-Discrimination Act, says he intends to introduce ENDA on Thursday, along with several other Republican and Democratic co-sponsors. ENDA would federally prohibit discrimination in hiring on the basis of sexual orientation or gender identity, and it has remained bottled up in Congress for a very long time. But Merkley and others believe ENDA’s moment may have finally arrived in the Senate – in part because of the dramatic shift in public opinion on gay rights, one typified by the sudden stampede of Democratic (and two Republican) Senators who have come out for marriage equality this year.

“We definitely see a tremendous amount of discussion of marriage equality,” Merkley told me today. “The momentum in that area will also be reflected in this area of employment. I feel we have reached a turning point.”

ENDA has remained bottled up in committee, despite the fact that it has over 40 co-sponsors, including two Republicans, Mark Kirk and Susan Collins. But Senator Tom Harkin, who chairs the Senate Health, Education, Labor, and Pensions Committee, has vowed to move the bill forward this year. Most observers expect that it will eventually come to the floor for a vote. “We’re ready to roll,” Merkley said.

The ENDA push comes at an interesting time for many Senators. The rapid shift in cultural attitudes on gay marriage noted by many observers — combined with the Supreme Court hearing two cases related to the issue — has led to a rapidly closing window for Senators to get on the right side of history on this civil rights question. But the looming ENDA debate poses some of them with a challenge: It’s one thing to endorse marriage equality, now that majorities support it, but it’s another for them to support federal legislation that would extend the push for full equality into other aspects of daily life. (The flip side is that ENDA doesn’t come freighted with the culturally charged aspects of the gay marriage debate.)

“If you support gay marriage, but you’re still not making the case that we should end discrimination, then you’re still essentially leaving in place a world in which LGBT Americans don’t have complete fair access to the job world,” Merkley said. “That makes a real difference in people’s lives. There’s little else in life that’s as important to the rhythm and well-being of self and family as access to employment.”

The ENDA debate creates a dilemma for Republicans: If conservatives filibuster the measure, it could resonate badly for the GOP at a time when even the RNC has conceded that generational shifts mean the party should reconsider its approach to gay rights. (Note that despite this concession, the RNC recently reaffirmed the party’s opposition to gay marriage.)

But presuming there is a GOP filibuster, does ENDA really have any chance of passage? Only two Republican Senators (Rob Portman and Mark Kirk) have come out for gay marriage; red-state Dems only embraced it reluctantly, and there are still three remaining Dem holdouts. Are there really 60 votes for ENDA?

Merkley insists the momentum in the culture will transfer to the Senate. “As folks have been wrestling with these issues of LGBT fairness, certainly having non-discrimination in employment is critical to equality under the Constitutional vision of the opportunity to pursue happiness,” he said.

Speaking of his fellow senators, Merkley added: “History is moving quickly, and they should join it.”

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UPDATE: I’m told that Dem Rep. Jared Polis and GOP Rep. Ileana Ros-Lehtinen will be introducing a similar bill in the House on Thursday, too.

Greg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant -- what you might call “opinionated reporting” from the left.