WASHINGTON — Marriage equality may have made tremendous advances over the past 20 years in the Senate, where half the chamber now supports it, but efforts to protect LGBT people from workplace discrimination have stalled.

In fact, while the Employment Non-Discrimination Act used to have much more support than the then-foreign notion of same-sex couples' marriage rights, marriage equality in 2013 has basically caught up in terms of Senate support — while ENDA hasn't gained much ground.

In 1996, only 14 senators were willing to oppose the Defense of Marriage Act — which bans federal recognition of same-sex couples' marriages and allows states to refuse to recognize same-sex couples' marriages performed in other places. At the time, The Washington Post pointed out this week, only three senators went so far as to publicly support marriage equality.

But ENDA — then a bill to ban sexual orientation-based discrimination in the workplace — was doing much better. A vote taken alongside the vote for DOMA saw ENDA fall only one vote short of Senate passage: 49-50.

That was the last time the Senate has voted on the measure, making it difficult to determine the exact level of support in the chamber. And while support for an idea — marriage equality — is easier done than endorsing or voting for a specific bill, the general comparison is nonetheless striking and emblematic of larger concerns among LGBT activists regarding the fact that ENDA, first introduced in 1994, has not been passed into law.

The most recent version of ENDA — which included protections for transgender workers, as have it has the past several times it has been introduced — was co-sponsored by 44 members by the end of 2012, and Senate Majority Leader Harry Reid was on record supporting the measure.

Although six of those members are no longer in the chamber, Sens. Martin Heinrich, Mazie Hirono, Christopher Murphy and Joe Donnelly all supported ENDA while in the House and are expected to support it in the Senate.

Additionally, Sens. Mo Cowan, Brian Schatz and Elizabeth Warren recently signed a letter supporting ENDA legislation, while Sen. Tim Kaine has said he supports ENDA and Sen. Angus King signed an LGBT employment nondiscrimination bill into law as Maine governor, bringing the total number of public supporters of ENDA in the current Senate to 48.

Although the addition of gender identity nondiscrimination protections to the bill more than 5 years ago was pointed to by some, including former Rep. Barney Frank, as leading to a need for further work before backers would gain more congressional support for ENDA, the lack of any real change in the level of senators' public support for the bill since 1996 is striking.

While marriage support in the Senate is roughly equivalent to public polling support for marriage equality, ENDA's co-sponsorship level lags significantly behind polling on the issue, which is somewhere around or north of 75 percent approval.

Marriage equality support has advanced so fast that the overlay of support for marriage equality and ENDA in the Senate are now almost identical.

Only one current senator who sponsored ENDA in the last Congress has not endorsed marriage equality: Sen. Susan Collins of Maine. And she is staying on the fence for now, having issued a two-paragraph statement to BuzzFeed recently that declined to support or oppose same-sex couples' marriage rights.

In addition to Reid, Sens. Max Baucus, Rob Portman, John Rockefeller and Jon Tester support marriage equality now but were not co-sponsors of ENDA in the 112th Congress. None of their offices returned requests for comment about whether they will support ENDA in this Congress.

Among Democrats opposed to same-sex couples' marriage rights, none of the five who served in the last session of the Senate — Sens. Tim Johnson, Mary Landrieu, Joe Manchin, Bill Nelson and Mark Pryor — were ENDA co-sponsors in the 112th Congress. Sen. Heidi Heitkamp, a new senator who opposes marriage equality, hasn't taken a public position on ENDA and a spokesman did not respond to an inquiry Wednesday.