A 2014 study by Virginia Tech Carilion Research Institute concluded that people who were more prone to disgust are more conservative. But, why?
Some scientists believe it's ancestral and that the adverse reactions were used to protect primitive ancestors from contamination and disease. This way a person wouldn't confuse drinking water with dirty pond scum.
The study measured participants' brain response to "disgusting" imagery using an MRI. The study could predict party affiliation with up to 98% confidence. The questionaire on chartsme.com uses Jonathan Haidt's disgust scale in lieu of MRI and imagery, so results are likely far less accurate. Watch TED Talk to learn more or read "Yuck!: The Nature and Moral Significance of Disgust".
As noted by some people who've emailed me, the results for this test will be skewed for people who work in industries where they deal with "gross" things on a daily basis. This includes, but is not limited to: doctors, nurses, childcare, military personnel and sanitation professionals.
Another book I highly recommend is "The Righteous Mind: Why Good People Are Divided by Politics and Religion" by Jonathan Haidt who created the disgust scale.