There are two types of successful unscheduled or late-announced events. You can blast it out there and generate viral buzz online and offline and hope that enough people change plans and come to the event impromptu, or you can have the event “happen” in the middle of an already-large gathering. The organizers of the Stevie Wonder “Get Out the Vote Early” event failed to do both and the results were predictable. The unannounced event in Cleveland was broadcast to 34,000 Twitter followers of the organization the morning of the concert. The hope was that Wonder would sing a song, then people would…