Over at Slate, Daniel Sarewitz cites a 2009 Pew Research poll that found only 6 percent of scientists are Republicans, while 55 percent are Democrats. According to Sarewitz, this poses a problem because several controversial scientific issues — such as global warming and embryonic stem cell research — are intrinsically tied to partisan policy positions.

But while Sarewitz looks into the potential political dilemmas of this trend, he doesn’t spend as much time focusing on the really interesting question: why are so few scientists Republicans?

Left-wing bloggers have come up with the predictably unconvincing responses (i.e., there are no Republicans in science because Republicans hate facts), but there may be a much more simple explanation buried in the original polling report. According to Pew, the survey’s sample of scientists was extracted entirely from the membership rolls at the American Association for the Advancement of Science:

Results for the scientist survey are based on 2,533 online interviews conducted from May 1 to June 14, 2009 with members of the American Association for the Advancement of Science (AAAS), under the direction of Princeton Survey Research Associates International. A sample of 9,998 members was drawn from the AAAS membership list excluding those who were not based in the United States or whose membership type identified them as primary or secondary-level educators.

And the society didn’t just provide Pew with its membership list. “[AAAS Director] Waylon Butler and his colleagues as AAAS were instrumental at constructing the sample of scientists and managing the recruitments of participants for the scientist survey,” says the Pew report.

This is important, because the AAAS is (as its name suggests) a political advocacy group. And, according to its website, the top issues it advocates for are climate change legislation, increased funding for the National Science Foundation, stem cell research, and green energy initiatives. Obviously, these aren’t the types of efforts that Republicans tend to support. It’s not hard to see why GOPers wouldn’t want to shell out the $146 membership fee to join an organization whose main mission is to advocate for issues they personally oppose.

So it makes sense that the Pew poll may be skewed in favor of liberal Democrats. But the question of where most scientists stand on the political spectrum is still worth looking into, and I’m curious to see what a broader study might show.