Update (7/18/11): Given that questions about the validity of Research 2000's polling remain unresolved, I've created a new version of the chart that appears in this post using data from other surveys:
Original post (8/10/09):
Since the release of a Daily Kos/Research 2000 poll showing that 28% of Republicans believe President Obama was not born in this country, Chris Matthews, Ann Coulter, Bernie Goldberg, David Paul Kuhn at Real Clear Politics, and other media figures have drawn an equivalence between the Kos poll and a 2007 Rasmussen poll which found that 35% of Democrats believe George W. Bush knew about 9/11 in advance.
The problem, as Media Matters points out, is that the wording of the Rasmussen poll ("Did Bush know about the 9/11 attacks in advance?") almost surely conflates people who believe Bush intentionally allowed an attack to occur with those who think the administration was negligent in its attention to the potential threat from Al Qaeda. Even National Review Online's Jonah Goldberg conceded this point in a column published soon after the poll was released.
There are also accusations being made following the 9/11 terrorist attack. One of these is: People in the federal government either assisted in the 9/11 attacks or took no action to stop the attacks because they wanted to United States to go to war in the Middle East.
When asked how likely this was, 16% of Americans said it was very likely and 20% said it was somewhat likely that people in the Bush administration "assisted in the 9/11 attacks or took no action to stop the attacks because they wanted to United States to go to war in the Middle East."
The partisan breakdown was not provided in the Scripps news report on the poll, but using the weighted data provided by Scripps (see update below), we can directly compare the proportion of incorrect or don't know responses to the 9/11 conspiracy and Obama birth certificate questions:
There is an undeniable symmetry to the misperceptions, which skew in the expected partisan directions in both cases. The total proportion of incorrect or don't know responses among Republicans on Obama's citizenship (58%) is comparable to the proportion of comparable responses among Democrats on a 9/11 conspiracy (51%).
The pattern of responses by party is similar if we only include those respondents who directly endorsed the misperception in question (i.e. "very likely" to be a 9/11 conspiracy, Obama not a citizen):
Even under this more stringent standard, 23% of Democrats and 28% of Republicans indicated direct support for the misperception of interest.
In short, using a more appropriate comparison poll, the primary conclusion stands -- both party's bases are disturbingly receptive to wild conspiracy theories.
Update 8/10 1:39 PM: I've updated the response totals and graphics based on data provided to me by Scripps that is weighted by race, age, and gender to match Census figures. Applying these survey weights results in slightly higher estimated levels of misperceptions on the 9/11 conspiracy question than I previously reported. This accounts for the discrepancy between the publicly available Scripps data and their published results that I mentioned in the initial version of this post.
Update 8/15 10:39 PM: I just discovered that the first chart had not been updated to reflect the correct weighted response totals. Apologies -- it has been corrected above.