So are the voting demographics changing or are people just getting sick of the war on drugs stuff? I figure it is mostly the first. However, I think at least part of it is a lot more people have tried marijuana than most think and don't consider it a dangerous drug.
I'd tend to say "all of the above"
Alaska legalized mostly because it isn't seen as a dangerous drug and a strong libertarian bent, combined with catching a lot of fence sitters with the promise of tax revenue from it. Given that we were entering a financial crisis at the time due to decreasing oil revenue, the idea of turning the financial cost of prohibition into a revenue stream tempted many. You also had the potheads voting to legalize it, of course. An earlier measure actually failed because the potheads voted against it, because, well, the measure sucked.
Meanwhile, like a decade ago when I was in North Dakota, I learned that something like 80% of the graduating high school class had at least tried MJ. It's definitely not seen as dangerous. Not as dangerous as alcohol and tobacco, in different ways.
edit: Reading up on them talking about "closing" the recreational loophole as seen in California where you just need to find the right doctor, I figure that doing that would only create a "state question" within 4 years or so just completely legalizing it.
And this makes it only FOUR states that don't have some level of legal medical use. Mostly passed by voter initiatives.
I really, really, wonder when the feds will break. I would NOT be surprised if it becomes an election issue next presidential campaign.