Reply #2: As Gman said

[SheilaT]

The right kind of polling, done correctly, is incredibly accurate. Some election cycles back all the networks did their own individual polling of "key" precincts, and it enabled them to call each state almost as soon as the polls closed. But more recently they stopped doing their own separate polling, pooled their resources and all such polling was done by Voter News Service (I think that's what it was called) who of course had it right in 2000, but took a huge hit for being correct. The result? No exit polling any more, which makes it much easier for evil people to steal elections.

Fifty years ago Isaac Asimov wrote an eerily prescient short story called "Franchise". It's in his short story collection Earth is Room Enough which is out of print, but can probably be found in a library or gotten on Amazon. Read it. It's about polling taken to its logical extreme.