A reader writes:
The poll cited by Ben Smith never asked if the respondents thought Bush was "complicit" in the 9/11 attacks. It asked, "How likely is it that people in the federal government either assisted in the 9/11 attacks or took no action to stop the attacks because they wanted the United States to go to war in the Middle East?" That's kind of a broad question, but it doesn't even mention Bush.
In any case, according to Smith, 22.6% of Democrats said "very likely" (another 28.2% called it "somewhat likely"). That's a far cry from the 45% of Republicans that give an unqualified "no" when asked if they think Obama was born in the US. And this, after incontrovertible proof has established that Obama was indeed born in Hawaii.
We are are talking about roughly the same period of time when anthrax from a US Government Army Research Lab was mailed to various high-ranking politicians. According to the FBI, a government employee was 100% responsible. Given that the FBI, along with most Democrats and Republicans, believe that the federal government was responsible for this terrorist act, is it really so "insane" that roughly 50% of Democrats thought it was at least "somewhat likely" that it could've played a role in another?
I think many people felt, especially after the "Bin Laden determined to attack inside the U.S." memo ruckus, that the administration was distracted at the wheel and therefore were passively complicit as opposed to directly, nefariously involved.
Ben Smith gives the impression that he is the first to reveal the details of this 2006 poll ("the University of Ohio yesterday shared with us the crosstabs"). However, this poll, including the crosstabs, has been commented on at length before – here for example. These articles demonstrate that although 50.8% of Democrats subscribed to some form of conspiracy theory regarding 9-11, the poll also showed that nearly a third of independents and nearly 20% of Republicans also believed in the 9-11 conspiracy theories. Unlike the birthers, the truther conspiracists were not exclusively Democrats. I also point out a recent article in Skeptic Magazine, "Who Still Believes in 9/11 Conspiracies? An Empirical Study on Political Affiliation and Conspiratorial Thinking" which concluded that truthers today are mostly right-wingers.
Finally, and really most importantly, truthers have always been the fringe of the fringe on the Democratic side. Truthers have been banned from Daily Kos since 2005. No reputable Democratic leader to my knowledge has ever given the slightest bit of credence to 9-11 conspiracy theorists. Obviously this is not true of the Republican party and birthers.
I particularly recommend Nate Silver's analysis on the difference betwen birthers and truthers.