Silver: Colorado could be willing to reverse gay marriage ban in 2010

Colorado voters will be ready to repeal the state’s constitutional ban on gay marriage next year, according to an analysis by voting statistics geek Nate Silver of

Following the Iowa Supreme Court’s establishment of same-sex marriage on Friday, Silver examined the trends in the 30 states that have voted on gay marriage bans and found that “while you might (not) know it from Proposition 8’s victory last year, voter initiatives to ban gay marriage are becoming harder and harder to pass every year.”

Unsurprisingly, there is a very strong correspondence between the religiosity of a state and its propensity to ban gay marriage, with a particular “bonus” effect depending on the number of white evangelicals in the state.

Marriage bans, however, are losing ground at a rate of slightly less than 2 points per year. So, for example, we’d project that a state in which a marriage ban passed with 60 percent of the vote last year would only have 58 percent of its voters approve the ban this year.

The 538 statistical model predicts California’s Proposition 8, a ballot measure to overturn same-sex marriage rights, would pass in 2008 with 52.1 percent of the vote, Silver said. That was almost exactly the vote the measure received.

Colorado voters passed Amendment 43, defining marriage as between one man and one woman, by 56 percent of the vote in 2006. By Silver’s analysis, that means the vote should be tied this year and opponents of a gay marriage ban should have a two-point edge in 2010. Since Colorado residents are becoming less religious as time passes, next year could be the year to repeal Amendment 43.

And that’s just what two proposed ballot measures working their way through Colorado’s tangled initiative process aim to do.

The trend has a downside for supporters of same-sex marriage. By 2012 nearly half the states should be ready to repeal gay marriage bans or at least decline to enact them, but some states in the Deep South are likely to take their sweet time. Alabama doesn’t look likely to favor gay marriage until 2023, and Mississippi, the last state to tip using Silver’s model, won’t get there until 2024.

Silver added the usual provisos about predicting social trends — for instance, there could be a backlash against same-sex marriage, slowing the movement, or, conversely, there could be a “paradigmatic shift in favor of permitting gay marriage,” accelerating the trend.

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