Friday, August 03, 2007

Bush Approval: DemoCorps 36-Pew 29-Trend 30.8

A new Greenberg Quinlan Rosner/Democracy Corps poll, taken 7/25-29/07 finds approval of President Bush at 36%, with disapproval at 60%. The new Pew Center poll, also taken 7/25-29/07 puts approval at 29%, disapproval at 61%.

With these two new polls the trend estimate of approval now stands at 30.8%.

The GQR/Democracy Corps poll is a statistical outlier, falling above the 95% confidence interval around the approval trend. At the moment we have two outliers-- ARG's 25% is below the confidence interval.

GQR/Democracy Corps polls are of likely voters, rather than adults as with most polls here. As a result, they consistently estimate approval levels higher than for the adult population and hence above the trend line as well. This is clear from the plot below showing "Greenberg" surveys tracking high. This is a "design decision" to survey likely voters, and should not be considered a defect in the poll. Inferences are to a different population from that of the general population.

The "house effect" estimate for GQR/Democracy Corps surveys is just below 3 percentage points, with a confidence interval from just under 2 to just under 4 points. Despite this substantial house effect, GQR surveys have only rarely exceeded the confidence interval for presidential approval.

As the number of recent polls has increased, the standard "blue line" estimator of support has increased it's "bend" and is coming closer to the more sensitive "red line" estimator, further evidence that approval trends changed direction around June 28, when the red estimator put approval at 28.7%. Currently the blue estimator agrees with that date as the turning point, though the estimate will continue to change until enough data are available for a stable estimate of the turning point.

While the change in support is now pretty clear, the reasons are less so. The timing coincides with a series of Supreme Court decisions, all carried by the majority created with Bush's appointments of Roberts and Alito. I don't think the Court is salient enough with the general population to be a strong driver of public opinion, especially of presidential approval. However, it is possible that the most politically involved conservatives were both aware of the decisions and gave Bush credit for his appointments, helping arrest his decline in the polls.

The other event about this time was the commutation of Scooter Libby's prison sentence on July 2. Initial reaction among the general population and even many self-described conservatives was disapproving of this decision. But here too the effect may have been positive among conservative Republicans and served to shore up support among that constituency.

But that said, unlike previous sharp turning points that have corresponded to major presidential speeches, this one is harder to account for with "obvious" actions of the President (or of Congress, for that matter.) I invite your speculation on this.