Here... Let me give you a source of pollster who explains just how crazy Cohn, Silver, Wasserman's polls were and how drastically they overshot.
This guy is right leaning, but no fan of Republicans, but the view here is that he's pissed about how poorly everyone did this and how it's incompetence or malice.
https://www.youtube.com/watch?list=PLHe3u4zZfY7K1N04z6Xu_JbY...
Watch from 30min to 40min. That's 10 minutes that I think will make the point with numbers that I can not make here.