What algorithm (formula) is used to compute the map?
In 2004, we ran three different algorithms. The main page just used the most recent poll. The second algorithm averaged three days’ worth of polls using only the nonpartisan pollsters. The third one included a mathematical formula for predicting how undecided voters would break based on historical data. The second one was most stable and gave the best final result, so this time a slightly variation of it is used: The most recent poll is always used, and if any other polls were taken within a week of it, they are all averaged together. This method tends to give a more stable result, so the colors don’t jump all over the place due to one unusual poll.