It also doesn't seem obvious to me that someone with a chemistry degree would have political goals more out of alignment with a hypothetical constituency than someone with a business or law degree.

STEM-folk are less likely to be religious. They are less likely to believe in certain pseudoscientific ideas as well, some of which affect politics (consider the anti-vaccination movements). They are also more likely to be knowledgeable of certain issues related to science and technology (quick, how many STEM people do you know who support TPP?) and therefore to take a different position on them or emphasize them to a different degree.