Fact: Academicians tend to be politically differentiated according to discipline, with those in the social sciences and humanities on the left, those in the natural sciences in the middle, and those in engineering and business on the right. Argument_ This is no coincidence. Studentsâ€™ political attitudes are being shaped by their professors. Counterargument_ Agreed. Itâ€™s not a coincidence. But the operative force is self-selection, not socialization
Having noticed this myself, my vote is that it is absolutely self-selection. It's no coincidence that the fields with the most earning potential (business, engineering) are populated by mostly conservatives, and that those with low earning potential (art, music, history) are liberals. It's the same reason that you don't see many liberals on Wall Street or conservatives working in art museums. Conservatives in the US just value money and power more than liberals, who may actually shun these things as "selling out".
The natural sciences have a mix of the two, due to the different career options. Conservatives are much more likely to want an big pharma or industry job, while liberals prefer to stay in academia and pursue basic science.
I'm not saying that this is true for all the grad students all of the time, but it certainly seems like an accurate depiction of the general trend.