… General election polling has historically been accurate because the rates at which different groups in the electorate turn out have been predictable across similar elections. Mid-terms looked a lot like other mid-terms and presidential years looked a lot like presidential years.
This all changed over the last three election cycles. …
The rumblings under the mountain of electoral stability that had been mostly ignored after 2008 and 2010 were followed by an eruption in 2012 and left a number of pollsters — especially Republicans — looking bad. [cont.]
Bryon Allen (WPA Opinion Research), Huffington Post