I've been rather surprised to see numerous comments this election cycle about Rasmussen's alleged Republican bias in polling data. This was a surprise to me, since I've always found Rasmussen's polling rather accurate, probably in no small part because of Rasmussen's finely tuned robocalling strategy. The rationale for the alleged bias — other than the higher numbers Republicans sometimes receive in Rasmussen's polling — seems to be two-fold: Scott Rasmussen provides analysis for Fox News and is known to be a Republican.
The first issue is circular, since Rasmussen's alleged bias factors into the analysis of Fox News's own bias. Is Alan Colmes biased towards Republicans, too? The second issue is a red herring. Every pollster is biased, but that doesn't really have anything to do with his data unless his data is shown to be inaccurate. A Fordham University professor looked at 20 major polls to see which one most accurately reflected the actual results of the 2008 Presidential Election and found Rasmussen and Pew to be the only ones to match the real results. Rasmussen consistently showed McCain-Palin as stronger than the other polls did, but that wasn't a bias — it was an accurate prediction of how actual voting would go.
I personally don't follow pollsters because I agree or disagree with them, but because I think this or that one gives me better data. Isn't that what most folks (other than a politicos looking to gain momentum) want from polling data?