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One question: People's opinions on things do change over time. Am I misinterpreting that you are, to some extent, arguing that polls taken two months before the election are somehow less valid because they did not end up matching with the final election results?

Nope. Voter surveys conducted AFTER the election showed most voters made up their minds a month ago. How come NONE of the polls caught this? This is another area where they didn't see voter behavior coming.

The study focuses on the accuracy of polls, not on their validity. My underlying premise is that the accuracy of most polls can't be proven. The value of this study is that these 20 polls were taken during a compressed period of time much closer to the election they were predicting than, say, polls that compare President Bush to a generic, unnamed Democrat more than a year out from the 2004 election. It's easier to evaluate these 20 polls for accuracy against the election as compared to presidential "approval ratings," for example. How can anyone prove their accuracy? Against what benchmark? Can't be done.

For a more in-depth answer to your query, look at the question: Do polls become more accurate closer to an election? The answer is that, in this study, they trended toward more accuracy closer to the election, but not strongly. Even at the end, only one poll got all five questions right within it's MOE.