Sen. Susan Collins (R-Maine) announced her support for gay marriage on Wednesday after landing an endorsement from the nation's largest LGBT advocacy organization in her bid for reelection.
"A number of states, including my home state of Maine, have now legalized same-sex marriage, and I agree with that decision," Collins said in a statement.
“Nearly 44 percent of Americans live in a state where same-sex couples can be legally married, and I believe this number will only continue to grow,” she said, adding that she never supported a national ban on gay marriage.
This is the third time the Human Rights Campaign has rallied behind the Maine lawmaker.
"Senator Susan Collins has played a pivotal role in advancing support for LGBT equality — from her dogged support for the repeal of 'Don't Ask, Don't Tell' to her critical vote for the Employment Non-Discrimination Act last year," said Chad Griffin, the group's president.
"HRC is proud to stand with Senator Collins, and with allies on both sides of the aisle like her, because she firmly believes that every American should be evaluated based on their abilities, and not who they love."
Sen. Rob Portman (R-Ohio) became the first GOP senator to publicly support gay marriage last year, after he revealed a change of heart when discovering his son was gay. Sen. Mark Kirk (R-Ill.) and Sen. Lisa Murkowski (R-Alaska) have also announced their support.
Collins’s announcement came on the same day that the 10th Circuit Court of Appeals became the first appeals court to rule that a state ban on gay marriage is unconstitutional. The ruling is being appealed to the Supreme Court.
A flurry of mostly Democratic lawmakers came out in support of gay marriage last year as the Supreme Court debated two cases regarding the issue, eventually striking down a portion of the Defense of Marriage Act.
Collins was suspected to be the next Republican senator in line to make an publicly support it. However, she continued to say it was an issue best left up to the states.
Last month, Collins also received the endorsement of her Senate colleague Angus King, an independent who caucuses with Democrats, and is favored in her bid against Democratic challenger Shenna Bellows.
--Mario Trujillo contributed to this report, which was updated on June 26th at 7:15 a.m.