Marriage rights for same-sex couples are now supported by a majority of the U.S. Senate, as three more Democrats added their endorsement.
The most recent backing came from senators Joe Donnelly of Indiana, Heidi Heitkamp of North Dakota and Bill Nelson of Florida, who all reversed their earlier opposition and endorsed the practice. That puts 53 senators on record in favor of extending marriage rights to gays and lesbians, including Republicans Mark Kirk of Illinois and Rob Portman of Ohio.
"This tidal wave of support for marriage equality in Congress reflects what we're seeing happening in the lives of everyday Americans around the country," said Michael Cole-Schwartz, a spokesman for the Human Rights Campaign, an advocacy group for homosexual rights. "People understand there's no reason to treat gay and lesbian couples differently than anyone else and it's crystal clear that the country is ready."
Four members of the Senate Democratic caucus -- Mary Landrieu of Louisiana, Tim Johnson of South Dakota, Joe Manchin of West Virginia and Mark Pryor of Arkansas -- remain in the opposition camp. Landrieu and Pryor face re-election in 2014. Johnson is retiring at the end of his current term in 2015.
Same-sex marriage advocates said momentum has been building since President Barack Obama and the Democratic Party platform backed the practice, as did voters in Maine, Maryland and Washington in November. A March poll by Quinnipiac University in Hamden, Connecticut, showed American voters backed gay marriage, 47 percent to 43 percent, a reversal from its July 2008 survey in which 55 percent were opposed and 36 percent were in favor.
The U.S. Supreme Court last month heard challenges to a California referendum that outlawed same-sex weddings and the federal Defense of Marriage Act, which prevents the federal government from providing benefits to married couples of the same sex. A ruling is likely by June.
"The country is on an evolution on this issue as are all of our elected leaders," Cole-Schwartz said. "Over time, as people continue to think about this, and as public opinion continues to go in our favor, you're going to see members change."
One Democrat, Manchin, said he would continue to oppose same-sex marriage.
"I believe that a marriage is a union between one man and one woman," he said in a statement. "My beliefs are guided by my faith, and I support the Defense of Marriage Act."
However, given increased Senate support for same-sex marriage, advocates plan a renewed push for a vote on legislation providing workplace protections for gay, lesbian and transgendered people, said Allison Hewitt, legislative director for the Human Rights Campaign.
Heitkamp said in a statement that she concluded that the federal government "should no longer discriminate against people who want to make lifelong, loving commitments to each other or interfere in personal, private and intimate relationships." She said she considered "the ability of anyone to marry as a logical extension of this belief."
In a statement sent to the Tampa Bay Times, Nelson said "the civil rights and responsibilities for one must pertain to all. Thus, to discriminate against one class and not another is wrong for me. If we are endowed by our creator with rights, then why shouldn't those be attainable by gays and lesbians?"
Donnelly said he had been rethinking his previous votes and positions. "In doing so, I have concluded that the right thing to do is to support marriage equality for all," he said in a statement. "We are a stronger country when we draw on the strengths of all Americans."
Two of the three senators, Heitkamp and Donnelly, represent states where Obama lost in the November elections.
"Red-state Democrats now see that this is not just a morally right place to be but a politically smart place to be," said Marc Solomon, national campaign director for New York-based Freedom to Marry.
Johnson's spokesman, Perry Plumart; Amber McDowell, a spokeswoman for Landrieu; and Michael Teague, a spokesman for Pryor, didn't respond to telephone calls and emailed requests for comment on the issue.
Supporters of same-sex marriage are calling and writing to the legislative offices of holdouts. The Washington-based Human Rights Campaign has changed its congressional grading to include a lawmaker's position on same-sex marriage along with his or her votes on other issues of concern to gays and lesbians.
Solomon said that gay and lesbian couples are trying to tell their stories directly to lawmakers and their aides, and through media coverage of unsuccessful efforts to get marriage licenses at county clerks' offices.
"Our approach is to continue to make our case through the telling of stories of loving and committed couples," he said.