By Jake Grovum

Colorado became the sixth state to allow civil unions for same-sex couples when Gov. John Hickenlooper signed the legislation Thursday. Another nine states and the District of Columbia allow same-sex marriage.

The Colorado bill, approved by the legislature after similar attempts failed in two previous sessions, was hailed by Colorado Democrats, even as some said they had hoped for a full legalization of marriage rather than civil unions. Ultimately, a handful of Republicans in the House -- where the measure failed in recent years -- voted to pass the bill, along with Democrats in both chambers who took majorities in the 2012 elections.

The state’s first openly gay House Speaker, Mark Ferrandino, led the push to pass the bill this year, telling members to “look at yourself in the mirror” as they considered the measure.

“Just make sure that you feel confident that you’re making the right vote and that you feel confident that that vote is something you will be proud of in the future,” he said. “I ask for an aye vote on Senate Bill 11, to honor love, family and equality.”

The civil unions law represents a significant victory for same-sex marriage supporters in the country’s western and Midwestern regions, where opposition has reigned. Colorado is just the second state west of the Mississippi River to approve a civil unions or same-sex marriage proposal on a legislative vote. Washington was the first. Iowa allows same-sex marriage, but only thanks to a state Supreme Court ruling.

Colorado’s move to allow civil unions also comes as same-sex marriage supporters see increasing momentum for their cause around the country. A recent Washington Post poll found all-time high levels of support for gay marriage.

Last year’s election in Minnesota marked the first time voters rejected a push to define marriage between a man and women in the constitution. Meanwhile, voters in Maryland, Maine and Washington approved same-sex marriage measures.

Nine states plus D.C. now allow same-sex marriage, while 35 either ban it constitutionally or through statute.

With the public mood shifting, advocates are playing offense. They have set their sights on overturning existing bans in states and pushing laws that would allow same-sex marriage or civil unions. Three states are seen as offering the most potential this year:

A move to allow same-sex marriage has already passed the Rhode Island House, and is stalled in the Senate. A vote is still possible before the legislature’s expected June adjournment.

A same-sex marriage bill has passed the Illinois Senate, but is tied up in the House. Democratic leaders there have said they’re about a dozen votes short of passage, but supporters, including President Obama’s political action arm, are pressing for approval.

In Minnesota, Democrats in control of both chambers are considering a same-sex marriage move, and at least one Republican senator has signed onto the measure. Bills in both the House and Senate recently cleared contentious hearings and await possible floor votes this session.

The Colorado civil unions measure takes effect May 1.