An example of how Real Clear Politics slants their polling "averages" to favor Republicans. [View all]
You may recall that yesterday I posted a new NBC/WSJ poll showing Democrats with a 6 point advantage in the generic congressional ballot.
However, you'll also note that the RCP "average" of recent polls shows Democrats holding just a 1.8% advantage over the Republicans in generic congressional polling. The devil, of course, is in the details. Here is their actual current polling and extrapolated average.
You may have already noticed that the NBC/WSJ poll is conspicuously absent. However, they do include a Rasmussen poll claiming that people want a Republican congress over a Democratic one by four points, the only pollster which has reported such a thing within the last six months. In addition, they make very sure to flag groups like Public Policy Polling as Democratic organizations, but don't do the same for the Republican-centric Rasmussen.
This is how Real Clear Politics slants their poll results: they deliberately exclude any poll which is too good for Democrats as an outlier, while making sure to studiously include any Republican-leaning outliers. By controlling what they DON'T include in their poll "averages," they can skew the results while still appearing completely above-board and impartial.