DENVER - Colorado, which was torn apart a decade ago by a debate over gay discrimination, is poised for another battle this fall over gay marriage - with some of the same people again playing key roles.

Four proposals dealing with one of the most divisive issues in the nation could end up on the Nov. 7 ballot, some aiming to cancel the others in a legal strategy of rock, paper, scissors. A key deadline looms Monday for petition drives.

This is familiar ground for Colorado, whose voters passed Amendment 2 in 1992 stopping cities from passing laws to protect gays from discrimination. Conventions were canceled and some threatened to boycott the state before the U.S. Supreme Court overturned the law four years later.

What will happen this fall is an open question.

Colorado has seen a flood of newcomers in the last decade and has had a mixed political history recently. It twice supported President Bush but in 2004 also awarded open House and Senate seats to two Democrats and put that party in charge of the Legislature for the first time in more than 40 years.

So far, a proposal to allow same-sex couples to register as domestic partnerships is the only measure assured a spot on the ballot.

The proposal would change state law. The author of Amendment 2, Wil Perkins, has responded with a proposed constitutional change to bar any new status similar to marriage (it would trump the domestic partnership plan should both pass).

Perkins, a retired car dealer from Colorado Springs, said the latest battle is about the same issue he saw at the heart of Amendment 2 - establishing special rights for gays.

Perkins said that will give gay couples the ability to push society to accept their sexual orientation. For example, he said, homosexuality could be promoted in sex education classes and parents wouldn't have any grounds to object.

The fight is about protecting traditional marriage, according to Perkins, who considers it the basis of civilization and the best way to raise children.

"It's not a matter of hatred or extremism. It's protecting a proven process," Perkins said. "They can live their lives any way they want to, but that doesn't give them any right to preferential treatment."

Coloradans for Fairness & Equality, a group backed by software millionaire Tim Gill, is backing the domestic partnership proposal.

But - get out the rock, paper and scissors - the group is also campaigning to add a constitutional amendment of their own stating that domestic partnerships are not marriage - just in case the Perkins measure is approved.

Evan Wolfson, a civil rights attorney and executive director of Freedom to Marry, said Colorado is the only state where voters could be given an alternative to an amendment barring gay marriage - and he doesn't think it's a good idea. He also fears voters will be confused.

"The public should not be asked to vote on the basic rights of a minority, particularly in a confusing bombardment of campaign ads and political agendas," he said. "What's wrong here is a minority is being asked to see its rights put up to a vote."

The pro-domestic partnership group unsuccessfully challenged the Perkins proposal in the Colorado Supreme Court, arguing it is too vague and could bar common law marriage or heterosexual, live-in couples from being able to agree on who will get property if they split.

The plaintiffs in that fight were Amendment 2 veterans: Jean Dubofsky, a former state Supreme Court justice who led the legal challenge against Amendment 2, and Pat Steadman, an attorney who worked on the case.

Steadman said banning gay marriage doesn't answer the question about what should happen to current couples.

"Gay couples exist. Like it or not, they have kids. The same things happen to them that happens to everyone else," he said.

The fight against Amendment 2 included a bumper-sticker slogan, "Hate is not a family value." Steadman said that was ineffective because it turned off people who don't approve of homosexuality and didn't try to help them understand discrimination faced by gays.

In contrast, the pro-domestic partnership campaign has been airing commercials showing a distraught man waiting in a hospital waiting room, unable to be at his partner's side. A voiceover concludes, "No matter who you are, commitment is commitment."

The clash between the old Amendment 2 foes has taken some of the attention off the fourth ballot measure, which would change the Colorado Constitution to ban gay marriage by defining marriage as being between one man and one woman.

The group leading that charge, Coloradans for Marriage, hasn't taken a position on the "similar to" proposal from Perkins.

Executive director Jon Paul said the group has concentrated instead on enlisting support from more than 250 churches across Colorado as it tries to gather signatures of 68,000 registered voters by Monday.

Paul said he is confident they'll be able to do it.

"Ours is a positive, straightforward message that most people latch onto," he said.