Yeah, I'm a poli sci/biochem double major too. The fact is, the poli sci major really helped keep me balanced academically; I really enjoyed the classes, and it gave me some non-science things to concentrate on for a change. I think it's best to choose to major in something you enjoy. If that happens to be biochemistry or some stereotypically pre-med major, more power to you. But if you enjoy political science, there is no reason why you shouldn't go with that. The bottom line is, if you enjoy yourself, you'll walk out of college having had a good time, and really, no one cares what you majored in when you apply.
As for handling the course load, at my school poli sci is a pretty wimpy major, and so it really wasn't too hard to do both the pre-med stuff and the poli sci together. As long as you plan it out early, you should be able to nibble away at both the pre-reqs and the poli sci major without too much trouble. Hope that helps!