again a 10 second search found many results.. of course there were many results of silly altcoins ICO announcements pretending to be votecoin systems, however actual discussions i found over 20 topics of meaningful discussion, with subsequent posts.. and separately many many posts not in topic of their thread but do mention details of a voting system using blockchain
however, to make it a learning experience for you.. ill just post you one of the earlier topics of the subject, and leave you to learn how to search
https://bitcointalk.org/index.php?topic=36807.0it not linked to provide substance, but more so linked because it shows how far back people have been talking about the idea, and that the idea has been talked about