I think increasingly, polls are proving fallible. I'm not sure people are willing to admit, even pseudonymously, what they really think and vote in the sanctity of the voting booth, for fear that they will be ostracized for not doing what they're supposed to do.
The main reason is probably the abandonment of landlines and phone books, and the adoption of caller id before it. It used to be easy to survey a representative sample of the population, and now it's impossible.
Possibly for polls during the campaign's, but exit polls, where people interview random samplings of people leaving the place where they cast their votes, have historically been very close to the actual vote results. In some areas of the US, the exit polls are spot-on. In other places, the numbers are off by a significant margin.
Some people try to explain it away by saying people vote for one candidate but are ashamed to admit it to a person asking them who they voted for, but wouldn't that tendency show up statistically across all precincts rather than in specific ones?
There is also an alarming number of times this occurs specifically in precincts with electronic voting machines.
It's not exactly "ashamed" I think, more like cautious. I mean, I've read multiple reports of people being beaten bloody on a candidate rally, so people would just prefer to stay out of trouble - even if they are proud of their choice, why they would risk talking about it publicly to random stranger? I mean, the pollster probably won't beat them up, but what if some crazy person overhears it and follows them and makes trouble? Nobody needs that. Sad, but such intolerance is part of the culture in US, many people just don't get "I disagree with you, but I respect your right to have your own opinion".
Eh, no need for shame, it could just be that one candidate appeals more to busy (or privacy-minded) voters who decline to be polled.
I generally avoid people with clipboards who are approaching people on the street, and I can believe that's something that correlates with opinions on other things.
