(Image Credit: Chip Somodevilla/Getty Images)

Three Democratic senators have reversed their stance on the Defense of Marriage Act in the past three days before the Supreme Court hears oral arguments on the law that limits marriage to one man and one woman.

Sens. Claire McCaskill, D-Mo., John "Jay" Rockefeller, D-W.V., and Mark Warner, D-Va., said today and Sunday that they no longer support a federal law banning gay marriage. The Supreme Court plans to hear oral arguments in a case challenging that law Wednesday, after it considers a law banning same-sex marriage in California Tuesday.

McCaskill made the announcement on her Tumblr blog Sunday.

"I have come to the conclusion that our government should not limit the right to marry based on who you love. While churches should never be required to conduct marriages outside of their religious beliefs, neither should the government tell people who they have a right to marry," McCaskill wrote. "Good people disagree with me. On the other hand, my children have a hard time understanding why this is even controversial. I think history will agree with my children."

McCaskill refused to take a hard stance on the issue in response to President Obama's coming out in favor of gay marriage in May, according to the Springfield, Mo.-based News Leader. The paper reported that she supported civil unions but had expressed opposition to same-sex marriage.

She was in good company. Only two Democrats in competitive Senate races publicly supported the president after his announcement.

Rockefeller was not facing re-election in 2012, but he would be next year if he were running again. The senator from West Virginia said in January that he plans to retire at the end of his term, leaving him just shy of three decades in office.

His statement today largely echoed McCaskill's.

"Like so many of my generation, my views on allowing gay couples to marry have been challenged in recent years by a new, more open generation. Churches and ministers should never have to perform marriages that violate their religious beliefs, but the government shouldn't discriminate against people who want to marry just because of their gender," Rockefeller said in a statement emailed to ABC News today.

"Younger people in West Virginia and even my own children have grown up in a much more equal society and they rightly push us to question old assumptions - to think deeply about what it means for all Americans to be created equal. This has been a process for me, but at this point I think it's clear that DOMA is discriminatory. I'm against discrimination in all its forms, and I think we can move forward in our progress toward true equality by repealing DOMA."

Rockefeller voted for DOMA when it passed under President Clinton in 1996. But in 2004, he voted against an amendment to the Constitution banning same-sex marriage, saying both his state and federal government already had laws limiting marriage to one man and one woman.

"I have heard from many West Virginians who are worried about morality in America," Rockefeller wrote after that vote. "They want to be sure that marriage is protected for themselves and for their children. I myself am not comfortable with same-sex marriage, and I want to assure every West Virginian that our definition of marriage - and our right to define marriage as we believe it - is not in jeopardy."

Sen. Warner announced his change of heart in a statement on his Facebook page.

"I support marriage equality because it is the fair and right thing to do," he reportedly wrote. "Like many Virginians and Americans, my views on gay marriage have evolved, and this is the inevitable extension of my efforts to promote equality and opportunity for everyone.

"I believe we should continue working to expand equal rights and opportunities for all Americans."

The three Senate Democrats join a long list of Republicans who have changed their minds about DOMA, many of whom now embrace the concept of gay marriage.

Sen. Rob Portman, R-Ohio, announced that he supports gay marriage, which followed his son's saying that he is gay. Several other politicians have referenced personal encounters with gay and lesbian family members as leading them to rethink their stances on the issue.

More than 80 upper-level Republicans also signed their support for same-sex marriage in an amicus brief for the Supreme Court last month.