It won't pass. And I say that as a paranoid, schizophrenic, tin foil hat wearing conspiracy theorists fuck-tard. Between the ease with which electronic voting machine fraud can be carried out...and the millions, nay BILLIONS of dollars that pharmaceutical companies could lose if Colorado's legalization efforts were just the beginning of a national trend (which it is) and that trend eventually gained momentum (i.e. multiple states legalize)...
I sincerely doubt that those with so much at stake would leave this election up to fair chance as decided by the people.