Nate Silver over at 538.com predicts that, if a marriage amendment makes it to the ballot in 2012 in Iowa, it's going to be a close battle:
So what does this mean for Iowa? The state has roughly average levels of religiosity, including a fair number of white evangelicals, and the model predicts that if Iowans voted on a marriage ban today, it would pass with 56.0 percent of the vote. By 2012, however, the model projects a toss-up: 50.4 percent of Iowans voting to approve the ban, and 49.6 percent opposed. In 2013 and all subsequent years, the model thinks the marriage ban would fail.
He included several factors, like the religiosity of the citizens in of state, as indicative of a state's ability to pass one of these amendments.
There are obvious issues with the model, like the fact that no state has ever rejected one of these amendments at the ballot booth so there isn't any evidence that these will start to be rejected (Arizona doesn't count anymore), state legislatures who are often required to start the ballot initiative process, and the fact that Iowa will have been performing same-sex marriages for almost four years before this referendum could even happen (which moved the numbers significantly in Massachusetts).
What do you all think? Any Hawkeyes want to weigh in?