What incentive is there for a politician to do the right thing on the whole? They need a broad professional support base (party) to succeed in the American voting system, which means they toe the line or go nowhere. And there are lobbyists (at best) pressuring or forcing their hand on decisions where so much money is at stake (private prisons, healthcare, education, etc).

You could say that a real character or charismatic leader may emerge from outside the political system and slowly convince people to change things, but the US just got the former and I don't know that it's working very well.

Brings to mind this recent story about Dwayne Johnson as a potential candidate: http://www.gq.com/story/dwayne-johnson-for-president-cover