The somewhat close result indicates either that readers of this humble blog aren't so ravingly liberal as you might think or that the issue of legalizing marijuana, even for medical purposes, doesn't break neatly along stereotypical liberal/conservative lines. Remember that one of the biggest advocates for IM 13, Bob Newland, is a red-in-tooth-and-claw libertarian who thinks the best government is just slightly more restrictive than the state of nature... and only during business hours.
I do sympathize with Mr. Newland on the issue of medical marijuana. I also enjoy the hay that can be made holding purported conservatives' feet to their own rhetorical fire: if you're all for government leaving us alone, and if you're incensed at the thought of government coming between you and your doctor, how can you not vote for IM13? You legalize medical marijuana, and you transfer power from government to doctors and patients. Those docs who dig dope can prescribe accordingly. Those docs who haven't come to that studied medical opinion can still direct their patients toward industrial pharmaceuticals and other non-herbal treatments. Why would any conservative want to see Congress, the Legislature, and the local sheriff making that decision instead of patients and their doctors?
By the way, I check stats from the government's Drug Abuse Warning Network and learn that nationwide in 2008, marijuana was responsible for 133,201 trips to the emergency room. Alcohol was responsible for 656,661 ER visits.
For deaths, I review this hefty DAWN report and count 1046 reported deaths linked to marijuana. The reporting metro areas include about 38% of the population, and DAWN notes some jurisdictions don't report marijuana as a specific cause of death. So multiply by 6: suppose there were really over 6000 marijuana-related deaths in 2008. The CDC reports that in 2007, alcohol was connected to 23,199 deaths.
And we don't even make you get a doctor's note to buy alcohol.