Church of the First Born up there indulges in polygamy, as do many others. And those motorcycle gangs?! What form of marriage do you call that.
I'm just looking at the big picture to predict how this would turn out if, heaven forbid apparently, the people get to decide. Bush carried those Idaho by 41 and 38 points in 2000 and 2004, respectively.
If bascially identical Amendments passed easily in Ohio and Michigan this year, (along with several others) then I think the people of Idaho would vote yes by even greater margins.