I'm surprised Aaron Strife didn't post this
http://www.nytimes.com/2014/10/30/upshot/why-polls-tend-to-undercount-democrats.html
its a really long article so i'll only cut the beginning piece out
http://www.nytimes.com/2014/10/30/upshot/why-polls-tend-to-undercount-democrats.html
its a really long article so i'll only cut the beginning piece out
Polls show that the Republicans have an advantage in the fight for control of the Senate. They lead in enough states to win control, and they have additional opportunities in North Carolina and New Hampshire to make up for potential upsets. As Election Day nears, Democratic hopes increasingly hinge on the possibility that the polls will simply prove wrong.
But that possibility is not far-fetched. The polls have generally underestimated Democrats in recent years, and there are reasons to think it could happen again.
In 2010, the polls underestimated the Democrats in every competitive Senate race by an average of 3.1 percentage points, based on data from The Huffington Posts Pollster model. In 2012, pre-election polls underestimated President Obama in nine of the 10 battleground states by an average of 2 percentage points.