Hours before President Obama made history on Wednesday by becoming the first sitting president to explicitly back same-sex marriage, presumptive Republican nominee Mitt Romney underscored his belief that marriage should be exclusively between a man and a woman.

After a bill that would have allowed same-sex civil unions stalled in the Colorado legislature, Romney told a Denver-based television station that he opposed extending equal benefits to gay couples.

I do not favor marriage between people of the same gender, and I do not favor civil unions if they are identical to marriage other than by name, Romney said in an interview with KDTR-TV. My view is the domestic partnership benefits, hospital visitation rights, and the like are appropriate but that the others are not. 

Romney expressed support for marriage equality at the beginning of his career, when he challenged Massachusetts Democratic senator Ted Kennedy. During that 1994 contest, Romney penned a letter to the advocacy organization the Log Cabin Club of Massachusetts in which he vowed to fight for gay rights and voiced his support for gays and lesbians serving openly in the military.

If we are to achieve the goals we share, we must make equality for gays and lesbians a mainstream concern, Romney wrote. My opponent cannot do this. I can and will.

But Romney shifted rightwards as he campaigned for governor of Massachusetts, saying he supported some rights for gays and lesbians, but opposing marriage and civil unions.

When the state's Supreme Judicial Court ruled in late 2003 that gays were legally entitled to marry, Romney responded with a statement reiterating his belief that same-sex couples should not be allowed to marry. He sought to block the decision, repeatedly seeking a stay of the ruling.

Marriage is an institution between a man and a woman, the statement said. I will support an amendment to the Massachusetts Constitution to make that expressly clear. Of course, basic civil rights and appropriate benefits must be available to people in nontraditional relationships, but marriage is a special institution between a man and a woman, and our constitution and laws should reflect that. 

From there, Romney has been consistent in his opposition to same-sex marriage. He has supported an amendment to the U.S. constitution that would say the only valid form of marriage is between a man and a woman and has sworn to defend the Defense of Marriage Act, a law prohibiting the government from recognizing same-sex marriage that Obama has ordered the Department of Justice to stop defending.