The Senate approved a proposal to grant Colorado gay couples legal rights similar to marriage after two days of emotional debate. The bill now faces its biggest challenge in the GOP-led House, which rejected the same proposal last year. Three Republicans joined all Democrats in approving the civil unions legislation on a 23-12 vote Thursday. Democrats spent months trying to persuade a House Republican to carry the bill but were unsuccessful. That doesn't bode well for the bill's chances. Supporters delivered impassioned speeches, saying gay couples lack important legal benefits. Some Republicans argued the measure undermines marriage. Republicans showed stacks of cards from constituents urging them to vote no. Democratic Sen. Pat Steadman, the bill sponsor, said the postcards are outweighed by constitutional rights.