A Republican lawmaker in Colorado bucked her party's stance on Monday and cast the key vote to advance a bill that would bestow the rights of marriage on unmarried same sex partners.

Speaking to The Colorado Independent, state Sen. Ellen Roberts (R) said it must have been her "libertarian streak" that convinced her to do it.

"I don’t think we should be in the business of legislating religion and morality," she reportedly added.

The legislation, which cleared the Colorado judiciary committee yesterday by a vote of 6-3, would authorize adults of any gender to enter into a "civil union" that carries the same legal rights as marriage.

The only real difference between permitting marriage equality and permitting civil unions is the name: a difference that some critics have suggested is akin to the "separate but equal" provisions in America's age-old, racist Jim Crow laws.

Roberts said she supported the bill because it would provide additional protections to children of gay parents.

The bill's sponsor, Sen. Pat Steadman (D), is himself gay and has said he would personally enter into a civil union with his partner, should the law allowed them to do so.

"This is a method of recognizing committed relationships between two people and allowing them to access the full scope of protections in Colorado law," he told reporters in February, shortly after introducing the bill.

Polling conducted by advocacy group Human Rights Campaign showed that a slim majority of Colorado residents are supportive of gay marriage.

The bill's next stop was to be a full debate in the Colorado Senate, where a strong majority of Democrats were expected to treat it favorably. Colorado Gov. John Hickenlooper (D) was endorsed by a number of gay rights groups in the lead-up to last year's election. He's since called civil unions a positive step toward strengthening equality and social stability in American society.

Colorado's constitution strictly defines marriage as an agreement between one man and one woman.