Do polls matter?

Perhaps I should say, how do polls matter? Polls are a form of data collection and have interesting geographical patterns.

Exit polls in an election are generally accepted to be very accurate because they record how people actually voted.

Other polls are more variable. If you ask people over 18 how they would vote "if the election were held today" you may or may not get a good prediction. First, longer time periods before the elction are less accurate than taking polls nearer the election, not just in the samer sense that it's harder to predict the weather in 3 weeks, but also because people exercise free will and the right to change their mind. Though interestingly, taken as a whole, these polls are better than you might think at making accurate predictions (though they might not predict particular winners and losers in tight races). A rolling average of say the last 3 months is quite good at recording overall conditions.

Second, pollsters use various "models" and don't actually just ask people of voting age. It's more accurate if you can get either registered voters or likely voters or at least a good proportion of these in your sample.

All this being said, a widely reported poll by CNN now shows that 61% of Americans--a new high--are opposed to the war in Iraq. It would be interesting to see how this breaks down at a more local level, and to see, for example, how it plays in places that are likely going to be important in November. The trouble is we don't know for sure ahead of time which places that will be (apart from generalities like "Ohio").

General polls however are only useful as far as they go, similarly general geostatistics characterize the population as a whole. Moran's I for example, is a general statistic and does not speak to local variation. Most of the interesting stuff however are the local differences--we live in that sense "locally."

This does not invalidate "global" polls, particularly when the President tries to characterize those against the war as Democrats (unless he accepts that 61% of the country is a member of the Democratic Party). But it does show we need to know the local situation on the ground before we make inferences about any given place.