“New Low” Update

Legacy blog posts President Bush

Charles Franklin has updated his job approval graphic to include the new surveys from the Pew Research Center and NBC/Wall Street Journal.  It is well worth reading in full, but here’s the money quote:

The effect of these and other recent polls is to lower my estimated
approval to 35.9%., down over 6 percentage points since the new year
began. A new low (with apologies to MP!) The difference between MPs
analysis of change in the individual polls and mine is that I’m
accumulating the evidence across all polls, and collectively they are
implying that the “true” level of support continues to fall. I’ve written previously on the problem of spacing between polls here.
At this point, President Bush’s approval is falling 1% each 12.5 days,
the most rapid decline of his presidency. If a poll has a 3% margin of
error, we’d only observe a statistically significant change in that
poll over a 38 day interval. Hence most changes in polls taken only a
week or two apart are not statistically significant even if they are
following the same rate of decline. The accumulated evidence across all
the polls is a better estimate of the trend in approval, and is
reflected in my blue trend line in the figure. Even
so, day-to-day movements are not statistically significant, so I agree
with MP that it probably shouldn’t be headline news that a “new low”
has been reached every day, simply because the trend is continuing
down.
By definition if the trend is down and you’ve passed the
previous low, then every day is a “new low”. Perhaps better to focus on
the trend than the new record lows.

This is Franklin’s graph (click on it to see the full-size version): 

As Robert Chung puts it in a comment on Franklin’s blog, this is “not a simple problem.”  I do wonder if the spacing of polls in this case helps create the impression of a gradual “week-to-week” sinking when the real change may have been an abrupt decline in late February in the wake of news about the UAE ports deal (beginning the weekend of Feb. 18-19) and about the chaos in Iraq following the bombing of the Samarra mosque (on Feb. 22).   When I looked at polls conducted between early December and Early February, I saw no trend in the Bush job rating.  Obviously, all of the polls conducted since mid February show a decline 3 to 8 points depending on the pollster.  The very few organizations that have polled twice since mid-February (which as of this morning includes an update from Fox News) also show no significant trend over the last 2-3 weeks.  If we connect the dots before and after mid-February — whether one pollster at a time as in yesterday’s graphic or with Franklin’s lowess regression — we get the impression of a steady decline.  But could that apparent gradual trend be just an artifact of the timing of the polls?

Mark Blumenthal

Mark Blumenthal is the principal at MysteryPollster, LLC. With decades of experience in polling using traditional and innovative online methods, he is uniquely positioned to advise survey researchers, progressive organizations and candidates and the public at-large on how to adapt to polling’s ongoing reinvention. He was previously head of election polling at SurveyMonkey, senior polling editor for The Huffington Post, co-founder of Pollster.com and a long-time campaign consultant who conducted and analyzed political polls and focus groups for Democratic party candidates.