Like all polling firms, Rasmussen Reports weights its data to reflect the population at large. Among other targets, Rasmussen Reports weights data by political party affiliation using a dynamic weighting process (see methodology).

During the final two months of the election season, we are updating these targets on a weekly basis to stay current with the public mood. While partisan affiliation is generally quite stable over time, there are a fair number of people who waver between allegiance to a particular party or independent status. The intensity of a campaign season may cause subtle changes in the partisan landscape as Election Day draws near.

The targets are not set arbitrarily. Rather, they are established based upon survey interviews with a separate sample of adults nationwide completed during the preceding six weeks. A total of 500 nightly interviews are conducted for a total of 21,000 interviews over the six week period.

This week’s adjustment shows a very slight increase in the number of Democrats, primarily offset by a decrease in the number of unaffiliated voters.

Results from this past week showed that the number of people considering themselves to Democrats spiked early in the week as the economic problems on Wall Street became visible. Overall, it was the best week for the Democrats since July. It remains to be seen whether this might lead to a lasting adjustment or be more of a bounce like that resulting from a party’s nominating convention.

For polling data released during the week of September 21-27, 2008, the partisan weighting targets used by Rasmussen Reports will be 39.0% Democratic, 33.5% Republican, and 27.5% unaffiliated. For the preceding week, September 14-20, 2008, the targets were 38.7% Democratic, 33.6% Republican, and 27.7% unaffiliated. For the first thirteen days of September, the targets were 39.7% Democrat, 32.1% Republican, and 28.2% unaffiliated.

This week’s adjustment will have little impact on the daily Presidential Tracking Poll. However, if the partisan trends continue shifting, it could have a significant impact as Election Day draws near.

During Election 2006, there was a notable shift in partisan identification favoring Democrats as Election Day approached. During Election 2004, there was a notable shift in the opposite direction. It is impossible to know which direction this will flow during 2008 (see month-by-month results). These shifts correctly foretold the election outcome in both years.

It should be noted that the current targets are fairly similar to the ratio that existed when Democrats won control of Congress in 2006. They are also fairly close to the make-up of the electorate in the Presidential elections of 2000 and 1996.

The current targets also suggest a significantly better environment for Democrats than they faced in Election 2004. When President Bush was re-elected, there were far more Republicans in the nation than there are today… and far fewer independent voters.

Outside of the election season, our baseline targets are established based upon survey interviews with a sample of adults nationwide completed during the preceding three months (a total of 45,000 interviews) and targets have been updated monthly.