Thse are graphs of various polls and bets on the Greek Parliamentary election of September 20, 2015.
Polls lately fail to predict the election outcome with the accuracy they used to. High "Undesided" numbers allow for what effectively means "anything goes" ;)
The source of the data is the document "Polls: GR Election 201509"; please feel feel to browse it and note your observations.
Update 23/9/2015: An interesting discussion on why polls fail recently, with some documentation, is taking place in Nikos Anagnostou's Facebook Wall.