
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.