Rasmussen, 6/26: "Why Polls Sometimes Show Different Results"

However, the challenge lies in finding the “right” mix of Republicans, Democrats, and unaffiliated voters. Some pollsters, including many academic and media pollsters, argue that partisan identification is fluid and changes frequently. This approach suggests that whatever partisan mix falls out from the results of a random sample is the “right” answer. In the case of the recent L.A. Times poll, this mix was 39% Democrats and 22% Republicans.

Polls that use this approach tend to produce a more volatile set of results (during Election 2004, one national firm reported results days apart that showed more than a ten-point swing in voter preference).

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At Rasmussen Reports, we address this issue by measuring changes in partisan identification on a monthly basis. We interview 15,000 people each month by telephone to dramatically reduce the level of statistical noise and get a stable result (see our latest partisan trends update and month-by-month numbers). This approach shows gradual shifts over time in keeping with the general flow of the political environment. During Election 2004, the GOP gained ground slightly as the campaign wore on. During Election 2006, the Democrats peaked at just the right time. Democrats struggled a bit (in relative terms) after taking control of Congress in 2007, but experienced a tremendous bounce during the early portions of Election 2008.

At the moment, our data shows that just over 41% of the population consider themselves to be Democrats and just under 32% are Republicans. We use the this information as the starting point for determining the mix of Republicans and Democrats in our national and state political surveys.