At least in the US, we see a lot of supposed polls used to try to sell you on an idea, rather than ask your actual feelings and views. There are so many polls and phone calls to people that they start to push back by providing misleading information.
It is also very difficult to estimate voter turn out. The weather was very mild, both candidates were very divisive in their politics, and both are very well known figures. You can see by looking at the numbers that the difference in votes is quite small both nationally and in many states.
People gave a lot of thought to their votes and turn out was quite high. The candidates very much targeted their audience and won their audience. Sanders might have actually won if he were the candidate, since he had a wider political appeal to centrist, but Hillary simply could not expand past her core audience.
Personally, I think that at least part of the voter push back was that Michael Bloomberg of NY is funding so many campaigns and issues across the country, and he is particularly unpopular outside of his very narrow base. He funds a lot of democrats (including Clinton) and requires them to take certain positions on issues, even if it costs them votes, or in this case, the election.
EDITED: 9 Nov 2016 16:16 by HARRYN