With everyone obsessing about polling, now would be a good time to take a look at their track record. The data from the two tables below is taken from the National Council on Polling. A review of the final National Polls from 1936 to 2000 is here. The final 2004 polling, both national and state, is here.
The track record for CBS in 2000 and 2004 is as good as anyone, good news given their latest result shows Obama up 51-42. In general polling is pretty good. A McCain win would by represent the biggest polling failure in history.
In the past this organization had done some excellent analysis of the state polling in 2002, 2004 and 2006. The detailed analysis for 2002 and 2006 are no longer on the site. However, the summaries that are there include the following data:
It would be shocking given this history for McCain to win any state where Obama's lead was over 5. In fact, it would be shocking for him to lose a state in which more than one poll showed him ahead. Examples of this rare occurancee include the 2004 Florida Presidential AND Senate races and the 2002 Georgia Senate race.