Just days after the U.S. Supreme Court allowed same-sex marriage rights to expand to more states, a new tally finds growing support on Capitol Hill for allowing gay men and lesbians to marry.

Growing support among lawmakers makes sense, given recent legal rulings and surveys suggesting a majority of Americans now support same-sex marriage. Congress is traditionally a lagging indicator of trends and public opinion. And yet, the jump in support over two years is notable, according to a new tally shared first with The Washington Post.

A new congressional score card set for release Thursday by the Human Rights Campaign, one of the nation's most prominent gay rights organization, finds that 45 percent of House and Senate lawmakers now support same-sex marriage -- a 12-point jump from just two years ago.

In the 100-member Senate, support has jumped considerably: 56 senators now support same-sex marriage -- 52 Democrats and four Republicans -- up from 36 senators two years ago. Forty-one of the 45 Republican senators oppose same-sex marriage. In the House, 188 lawmakers and non-voting delegates back gay marriage, up from 143 two years ago.

"We're seeing significant increases in support. In some sense, the scoring gets harder as members get better," David Stacy, HRC's government affairs director, said in an interview with The Washington Post.

Of the 541 members of the House and Senate, including nonvoting delegates, HRC gave 210 members a perfect rating, up from 139 in the 112th Session of Congress.

A record-breaking 169 House Democrats and 39 Democratic senators earned perfect scores from the group this year. Just two House Republicans -- Ileana Ros-Lehtinen (R-Fla.) and Richard L. Hanna (R-N.Y.) -- scored 100 percent. No Senate Republicans earned top scores.

Here's how support in the 113th Congress compares to the previous session:



Courtesy of the Human Rights Campaign.

And here's a more specific breakdown in each chamber:



Courtesy of the Human Rights Campaign

"The real story from this scorecard is the movement of Democrats to go from supportive to 100 percent supportive. That's the big movement," Stacy said. "It's really Democrats who were in the '80s and '90s are now with us 100 percent of the time and feel like this is not only the right place to be politically but also the right thing to do."

Support among Republican lawmakers remains low, but a majority of Republican voters nationwide oppose allowing gays and lesbians to marry.

In addition to tracking support for marriage rights, the HRC scorecard measures how lawmakers voted and acted on several key bills. In the House, that includes supporting the renewal of the Violence Against Women Act, which for the first time barred discrimination against victims based on sexual orientation or gender identity; voting to increase federal housing funding for people with AIDS; and cosponsoring the Employment Non-Discrimination Act, the Respect for Marriage Act and other bills. In the Senate, scores accounted for support of those bills and whether senators voted to confirm three openly gay Obama administration appointees.

While a majority of Republicans fare poorly, Stacy noted three who demonstrated notable shifts. Rep. Chris Gibson (R-N.Y.), facing a well-funded challenge from Democrat Sean Eldridge, jumped from a 0 score in the last Congress to 76 percent this session. Rep. Mike Fitzpatrick (R-Pa.), who represents suburban Philadelphia and is also a perennial Democratic target, went from 5 to 68 percent. And Rep. Frank LoBiondo (R-N.J.), also facing Democratic pressure this year, jumped from a 0 to 76 percent this year.

"You're looking at Republicans in moderate districts who are trying to appeal to moderate voters, women and millennials," Stacy said. "When they look at these issues, being pro-equality is a plus and being anti-equality is a minus."

Among Senate Republicans, Alaska's Lisa Murkowski is tops, at 88 percent. She's followed by Sens. Susan Collins (R-Maine), with 85 percent, and Mark Kirk, with 78 percent. Murkowski's score jumped from 47 percent in the last congressional session, mostly because she voted for ENDA.

There were notable jumps among moderate Democrats, also. Sen. Mark Warner (D-Va.) jumped to a 95 percent rating, a 19-point jump. Sen. Kay Hagan (D-N.C.) also scored 95 percent, up from 66 percent.