Profit or loss is generally the small difference between two large numbers. That being the case, a small accounting mistake will often make a big difference in determining profitability. And so, while we may sympathize with the difficulties faced by accountants, we surely would not want to hire one if she regularly gave us bogus information about whether our enterprise was making money or losing money.
That is entirely analogous to the situation we face this week, and going forward, with the business of professional polling. Because we live in a closely divided country, and winning or losing elections is a matter of the small difference between large numbers.
What went wrong with the polling? Obviously, I don’t know.
All we normal people have to aid our understanding is our gut feeling. My gut feeling is that the right of center half of the country is significantly less inclined to answer pollsters than the left of center half of the country.