It cannot be said enough. Nationwide, as people's education level increases, they are more likely to vote Republican, through the master's degree level. People with Ph.D's make a sharp turn to the left, however. I suspect that Ph.D's are statists who want to preserve the status quo which favors paper crendentials over experience and results. (Teachers should make less than truck drivers.)
Good point, PhD's are generally professional students, graduate degree types are generally out working.
Depends on the field: Ph.D.'s in areas where you are expected to be able to DO something (Engineering, Computer Science, Business, and so forth) are much more likely to be conservative than those in which there are no right answers (Humanities and Social Sciences, Education, Art, etc.).
No. The reason is that the overwhelming majority of Ph.Ds are professional academics with doctoral degrees that wouldn't be worth a dime in the real world. Those degrees are only of value inside their cloistered little group-think world.