DENVER (AP) - A measure to give same-sex couples in Colorado rights similar to married couples faces its first floor debate of the year.

The measure has simmered in the state Legislature since January. Its approval in the Democratic Senate seems assured because it passed 23-12 last year. But it's still unclear whether the GOP House will agree to civil unions in the final weeks of the 2012 session.

Senate Bill 2 has some support among Republicans. But gay rights activists say the measure could again be defeated in the Republican House. Last year, a similar civil unions proposal cleared the Senate but failed by a single vote in a House committee controlled by the GOP.

Colorado voters rejected gay marriage in 2006.