Courtesy of MSNBC
The latest was perhaps the most significant, as Alaska Sen. Mark Begich said in a statement Monday night that he now supported same-sex marriage.
"Gay and lesbian couples should not be denied the ability to pledge their love and commitment through the civil institution of marriage," Begich said, according to BuzzFeed. "I believe that two committed adults of the same sex should be able to receive a government-issued marriage license, while religious institutions retain their right to determine which marriages they will perform."
As a red-state Democrat up for re-election in 2014, Begich's turn marks the most meaningful political reversal in a Congressional group that also includes Missouri Sen.
Warner made his announcement on his official Facebook page Monday.
"I support marriage equality because it is the fair and right thing to do. 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," Warner said.
McCaskill, meanwhile, took an unconventional approach by announcing her shift on her Tumblr. It was a significant "evolution" from her position during a high-profile campaign in Missouri, when she said that the issue should be left up to individual states.
"My views on this subject have changed over time, but as many of my gay and lesbian friends, colleagues and staff embrace long term committed relationships, I find myself unable to look them in the eye without honestly confronting this uncomfortable inequality," McCaskill said in the statement.
"Supporting marriage equality for gay and lesbian couples is simply the right thing to do for our country, a country founded on the principals of liberty and equality. 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."
Other prominent present and former politicians have in recent weeks announced their support for same-sex marriage, including former Secretary of State Hillary Clinton. And just more than a week ago, Ohio Sen. Rob Portman became the first sitting Republican Senator to endorse gay marriage.