If Colorado’s 2006 gay marriage ban were put before voters again next year, would it pass? Nate Silver says “no.” He’s the stats guru who won nationwide acclaim last year for the political forecasting on his website, FiveThirtyEight.com. But Silver has calculated that Colorado would vote down a gay marriage ban as soon as 2010.

He used a formula that takes into account when a gay marriage ban is introduced, voters’ religiosity, and the number of evangelical voters in the state. Of course, since a gay marriage ban is already on the books in Colorado, Silver’s prediction means little in practical terms. But if true, it would mean a startling shift in voter sympathies since 2006, when Amendment 43 passed with 56 percent of the vote. Referendum I, which would have established domestic partnerships, was shot down at the same time by 53 percent of voters. But a move to the left on the issue of gay marriage would reflect a general nationwide trend. In the past month, both Iowa and Vermont have legalized gay marriage. Massachusetts and Connecticut also allow same-sex marriage. The Washington, D.C., City Council voted earlier this week to recognize same-sex-marriages from other states. Pollster Floyd Ciruli thinks the political climate has changed in the state over the past three years. Democrats are now solidly in control of state politics–and unlike in 2006, a gay marriage initiative would likely win support from the vast majority of the Democratic political establishment. Still, he’s reluctant to concur with Silver’s prediction that Colorado voters would oppose a gay marriage ban as soon as next year. Coloradans are likely to be given an opportunity to answer that question by next year, as efforts are under way to put two measures on the ballot: one to allow gay marriage, the other to permit civil unions.