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Bush Approval: 4 New Polls, Trend up to 34.7%

Topics: George Bush

1BushApproval2ndTerm20070311.png

Four new polls have come in since Friday, lifting President Bush's approval trend estimate to 34.7%, from last week's 33.4%. The new polls are AP/Ipsos (3/5-7/07, 35% Approve/65% Disapprove), CBS/New York Times (3/7-11/07, 34%/58%), CNN/ORC (3/9-11/07, 37%/57%) and LATimes/Bloomberg (3/3-11/07, 38% Approval, the disapprove rate has not yet been released.) With four polls all coming in above the previous trend estimate, the evidence favors an increased approval rate over last week. However, there remains quite a bit of noise in the estimates.

The new CBS polls shows approval of President Bush from Republicans rising substantially since January, when it was 63% to 65% in February and 75% in the latest poll. One advantage of a Democratic Congress for the President is it gives his partisans an opponent to blame, and may as a result help improve the President's support among Republicans. We'll have to look into this a bit more systematically.

For a full description of these graphs, please see this earlier post.

The last six polls appear below.

2LastSixPolls20070311.png

With the new estimate of approval, all four new polls (and indeed, all of the last six) are pretty close to the estimated trend. This at least means that no single outlier is unduly influencing the current estimate.

The residuals, deviations around the trend, are shown below. (Note that the CBS/NYT poll that appears outside the lower 95% confidence limit is an older poll from 2/23-27/07, not the latest one. That one has been inside the confidence interval until recent polling revised the trend up a bit. This kind of dynamic is common until more than a dozen or so polls are available after any single date.)

3BushResiduals20070311.png

To assess the variability of the trend estimator, I run 20,000 bootstrap samples of the approval series, and estimate the trend 20,000 times. The gray region below shows all these samples, while the blue line is the current estimate.

4BootApproval20070311.png

It is worth noticing that the spread of estimates over the past two or three months has been a bit wider than earlier parts of the series. In part this reflects an intrinsically greater uncertainty of the estimate at the end of the series. However, it also seems that the approval polling since the November election has also been a bit more variable than in most of 2005-06. Whether this reflects a plateau in approval with more randomness around a roughly stable mean, or if the shift to a Democratic congress has allowed for more variability is an interesting question.

Finally, we can take out each of the last 20 estimates and see how sensitive the trend has been to these polls.

5Sentitivity2ndTerm20070311.png

There has been quite a bit of variability, foretold by the bootstrap results, over a range of about 5 points for the trend estimator. That's a lot less than the range of polls, as you can see dramatically in the figure but still shows that the trend estimate is itself subject to uncertainty.

Cross-posted at Political Arithmetik.

 

Comments
m hill:

I was looking at the pdf of the NYT/CBS poll's results. It says N = 1362, Republican N = 698. Isn't that a bit Republican heavy? Aren't 20 some percent independents, and 30 some percent Democrats or Republicans?

http://graphics.nytimes.com/packages/pdf/national/20070313_pollresults.pdf

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The CBS/NYT poll included an oversample of Republicans so they would have more analytical power looking at the Republican subgroup. The 698 Republican respondents are weighted down to 362 for the analysis of the population as a whole. The weighted proportions are 26.6% Rep, 34.6% Dem and 38.8% Independent. According to the CBS/NYT release "The results were then weighted in proportion to the average party distributions in previous 2007 CBS News and CBS News/New York Times Pols." That seems sensible to me.

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The CBS/NYT poll included an oversample of Republicans so they would have more analytical power looking at the Republican subgroup. The 698 Republican respondents are weighted down to 362 for the analysis of the population as a whole. The weighted proportions are 26.6% Rep, 34.6% Dem and 38.8% Independent. According to the CBS/NYT release "The results were then weighted in proportion to the average party distributions in previous 2007 CBS News and CBS News/New York Times Pols." That seems sensible to me.

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