Approval of President Bush has slipped to an estimated 33.4%. The new estimate adds a new poll from American Research Group (ARG) taken 3/18-21/07 with approval at 32%, disapproval at 63%.
(For a full discussion of the plots and how to interpret them, see this post.)
The approval trend has fluctuated between 33.0% and 35.5% over the past 20 polls. Some of this variation is sensitive to whether the latest poll is above or below the current trend estimate. At the moment, the most recent polls have run below the trend, and that has pulled the estimate down. None of the recent polls qualifies as an outlier, so the current estimate is unlikely to be driven by a single exceptional case. However, the fluctuations in the estimate mean that we are safest saying that approval is currently in the 33%-35% range. The trend estimate's variation is considerably less than the range of polls, as the last plot below makes vividly clear. This is an example of what we can gain in precision by using estimators that combine data from many polls, rather than relying on any single poll.
Cross-posted at Political Arithmetik.