Actually I think it has more to do with the fact that the markets do not like uncertainty. They did not like when W was president and Congress was Republican held. The more fighting there is between the pres and congress the more they like it. It means less gets done. It means there is less volitility in the laws and regulation. With one party in control of both houses of congress and the presidency, the fear is that they can get more done. Getting more done makes investors a little jumpy.
"I would rather be exposed to the inconveniences attending too much liberty than to those attending too small a degree of it." Thomas Jefferson