Actually you can't survey the entire population. But you can increase the sample size, within reason.
But you're right, the quality of the sample is questionable - and most times they don't take the necessary care with that. Which is why Silver's Bayesian method is much better.
"The liberals can understand everything but people who don't understand them."
Lenny Bruce
"The cleverest of all, in my opinion, is the man who calls himself a fool at least once a month."
Dostoevsky
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