OK, for it to be a real dark horse the song cannot be high in the betting as they would be considered the 'favourites'. So that rules out France, UK, Estonia, Hungary, Azerbaijan, Sweden (surprisingly, as it's rubbish), Germany, Bosnia & H, Russia and Ireland who are the top 10 in the betting and all 20-1 or under, so can't really be considered 'dark horses'.
Outside of them, I would offer 3 songs as potential dark horses and my reasons
Turkey - Seems to be largely forgotten but is a good solid rock song, they perform it well, Turkey get many diaspora and neighbour votes and generally do well with the juries. You can get 66-1 on this for top 4, a pretty good bet in a weak year.
Austria - For me this is the best ballad in the competition and has a fantastic ending. She is a very good singer and if is lucky to be near the end in the draw could make an impression. Not a winner, but could sneak top 4 at good odds.
Denmark - Again, largely written off, but for me this is a very good torch type song, well sung. It would definitely need to be right at the end of the draw to make a big impression but a good each way bet for me.
Outside of them, I would offer 3 songs as potential dark horses and my reasons
Turkey - Seems to be largely forgotten but is a good solid rock song, they perform it well, Turkey get many diaspora and neighbour votes and generally do well with the juries. You can get 66-1 on this for top 4, a pretty good bet in a weak year.
Austria - For me this is the best ballad in the competition and has a fantastic ending. She is a very good singer and if is lucky to be near the end in the draw could make an impression. Not a winner, but could sneak top 4 at good odds.
Denmark - Again, largely written off, but for me this is a very good torch type song, well sung. It would definitely need to be right at the end of the draw to make a big impression but a good each way bet for me.