I know there are those who would argue that the balance of house and senate seats is to provide this, but usually the way the system works here is that whichever party(ies) control Congress and the Presidency have sway (of course, we now have the Executive and Legislative branches under opposite parties, which generally makes for a moderate period), swinging things either conservative or liberal, where it appears from the popular vote that a much more moderate approach is desired — that is, it is in only a very few cases where "major" elections are lopsided (I personally don't consider even 60%-40% lopsided — 40% is a significant amount of people), but that small push in either direction is more like a knife-blade than a scale.
If this is the case, are there any chaos-theory works to describe politics. After all, a very small changes in input — the popular vote — seems to cause large swings in the social environment? What about when the inputs fluctuate back and forth across party lines? And, since I've not been able to find any, are there any systems which can more adequately implement a more broad continuum of political interests than the present system?