Sens. Heidi Heitkamp (D-N.D.) and Joe Donnelly (D-Ind.), both hailing from deeply red states, announced on Friday their support for gay marriage. 
 
 "In speaking with North Dakotans from every corner of our great state, and much personal reflection, I have concluded 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," Heitkamp said in a statement. "I view the ability of anyone to marry as a logical extension of this belief. The makeup of families is changing, but the importance of family is enduring." 
 
 "In recent years, our country has been involved in an important discussion on the issue of marriage equality," Donnelly said on Facebook. "While serving in the House of Representatives, I had the opportunity to act on a core belief of mine: we are a stronger country when we draw on the strengths of all Americans. I voted to repeal ‘don't ask, don't tell’ and was an original supporter of the bill that would make it illegal to discriminate against someone in the workplace because of their sexual orientation." 
 
 "It is also for that reason that I oppose amending either Indiana’s or our nation’s constitution to enshrine in those documents an 'us' and a 'them,' instead of a 'we,'" he continued. "With the recent Supreme Court arguments and accompanying public discussion of same-sex marriage, I have been thinking about my past positions and votes. In doing so, I have concluded that the right thing to do is to support marriage equality for all." 
 
 Heitkamp and Donnelly join several other Democratic senators who have recently made statements backing marriage equality, including Sen. Tom Carper (D-Del.) and Bill Nelson (D-Fla.). Support from Heitkamp and Donnelly is particularly notable, however, because both come from states that voted for Mitt Romney in 2012 and generally elect Republicans. However, neither face reelection until 2018, and if public opinion continues its dramatic shift in favor of same-sex marriage, the issue may become less controversial. 
 
 Only four remaining Democratic senators have not publicly backed gay marriage: Mark Pryor (D-Ark.), Joe Manchin (D-W.Va.), Mary Landrieu (D-La.) and Tim Johnson (D-S.D.). Landrieu and Pryor face re-election in 2014 in Southern red states. Johnson is retiring in 2014, but there is a movement to draft his son to run for his seat. Manchin, like Donnelly and Heitkamp, is not up for reelection until 2018. ||||| (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.
– Add two more senators to the list of gay-marriage "evolvers"—North Dakota's Heidi Heitkamp and Indiana's Joe Donnelly said today that they support same-sex marriage, reports the Huffington Post. Both are Democrats from conservative states and both are safe from re-election campaigns until 2018. "The makeup of families is changing, but the importance of family is enduring," said Heitkamp in a statement. Together with yesterday's flip by Florida's Sen. Bill Nelson, the moves leave only four Democratic senators who have not publicly voiced support for gay marriage. If you're a bit amazed by how quickly senators have been "evolving" on this issue, you're not the only one. But Nate Silver decided to take things a step further, as usual, and try to come up with a mathematical model to explain why, for his latest blog post in the New York Times. The key, says Silver, is public support for gay marriage in many states growing from a slight majority to a clear one. But he expects the pace to slow down greatly at this point. "The remaining senators who have not taken the opportunity yet may have good political reasons for it, and may wait some time before they do," he writes.