A lot of it is voodoo.
1. How do you poll people who only have cell phones?
2. How do you sample so that it represents people who will vote.
3. How do you account for voter enthusiasm?
The pollster’s preconceptions will determine a lot of that.
Heck how many people even answer the phone anymore if they don't recognize the number? I don't...if they leave a message they need to talk to me, if they don't they don't. They're either getting technologically challenged people, lonely people or people who have a lot of time on their hands.