i think you should include it too...it looks good. but maybe you could think of a way to be sort of vague about it. Like could you say you were the "Marketing Intern" or whatever with the "government department" or "California State Governor" or something along those lines where you can include your experience without saying which party you worked for?
If the experience shows a surprising level of responsibility, find a way to include it. If it was something more like fetching coffee and making copies, be more general.
Agree with what most have said...as long as you separate your duties from your beliefs it should be fine. It looks like you ave a good grasp on when to talk politics and when to leave them at the door.
__________________
IIII IIII IIII
"A child of five would understand this. Send someone to fetch a child of five."
Groucho Marx