

Sen. Susan Collins (R-Maine), ranking Republican on the Senate Homeland Security and Governmental Affairs Committee walks to a meeting on Capitol Hill in Washington, Wednesday, Nov. 28, 2012, for a meeting with UN Ambassador Susan Rice. Rice continued her fight Wednesday to win over skeptics in the Senate who could block her chances at becoming the next U.S. secretary of state, while Republican lawmakers said they were even more troubled after face-to-face meetings with her over the handling of the Sept. 11 deadly attack on the U.S. Consulate in Benghazi, Libya. (AP Photo/ Evan Vucci)

Sen. Susan Collins (R-Maine) has announced her support for same-sex marriage, making her the fourth sitting Republican senator to do so publicly.

"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, adding later: "I have long opposed efforts to impose a federal ban on same-sex marriage. In both 2004 and 2006, I voted against amendments to the United States Constitution that would have banned same-sex marriages by preempting state laws."

Collins joins three other Republican senators who publicly support gay marriage: Lisa Murkowski (Alaska), Rob Portman (Ohio) and Mark Kirk (Ill.).

Collins faces reelection this year. She is heavily favored to defeat Democrat Shenna Bellows.

On Wednesday, Collins was endorsed by the Human Rights Campaign, a gay rights group.

“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, to her proud support for marriage equality,” Chad Griffin, president of the Human Rights Campaign, said in a statement backing her.