I can also see why polls conducted during the weekends are so varied from weekday polling. I get something like 90% no answers or answering machines on Saturdays but nearly 50% answers on weekdays.
I'm starting to wonder if polling is headed the way of the buggy whip precisely because of the proliferation of communications technology.
What people tell you on a phone today has lost all correlation with what people who get in their car and drive to a polling place will do in the booth.
Early on when bells rang and people politely answered the door/phone, polling worked. Now that caller id, do-not call lists, voicemail (how many people really still have landlines with answering machines!), unlisted numbers, cell phones with all the above... etc....even if you can reach them, the proliferation of these "communications curtains" implies that people don't politely want to talk to others, possibly particularly strangers!
There is SO MUCH NOISE in the data now, the filters used to recover the signal are recovering whatever the filter designers choose!
So I think society is headed in a way where pre-polling and exit-polling is going to become relatively useless.