General Discussion
In reply to the discussion: Are POLLS reliable these days? [View all]Yo_Mama
(8,303 posts)Voter turnout in 2012 was 57.5%. Sometimes it is around 60%, but that only occurs in presidential election years. So if you can't screen out the percentage of people who won't show up at the polls (or mail in the ballot), your poll is bound to be off.
But voter participation changes for reasons that are not always obvious to pollsters. Every polling firm has an independent algorithm, which the firm tries to rebalance each cycle based on what was off the previous cycle. So minor changes in voter sentiment can change the vote tallies quite a bit from polling. It is impossible to get likely voterhood exactly right, no matter how many polling questions you include.
Also, people who are embarrassed about not voting or not having voted might lie to the pollsters.
Also, likely voter assessments become much more accurate late in the election cycle.