So are you saying that because a different candidate can get elected each time round perhaps even from different parties that means that these people can not serve the interests of the same dark and powerful forces?

I think that I'd rather assume that candidates, both before and after their elections, give much more than lip service to the interests and beliefs of the people who elect them, and that they do not "serve the interests of dark and powerful forces" at all. For that matter, I've never seen any reason to believe that "dark and powerful forces" even exist outside of the pages of Batman comics and the fevered imaginations of a few people who have nothing worthwhile to do with their time.