It'll pass. Like I said earlier in the thread, every time gay marriage is voted on directly by the people, it fails. If this fails, it won't legalize it though, right?
Well, this actually bans a lot more than gay marriage (and won't legalize it if it fails). Even some of the sponsors have admitted it would likely be appealed in 20 or so years, though there'll be plenty of time where most of the public will want it overturned but won't yet have a legislative supermajority required to actually overturn it.
