Only marginalized outsiders like Tom Tancredo, Ron Paul, and Tom Coburn. Once they get sucked into the playing Great Appropriations and Committee Chairmanship Game, they all become compromised at some level, and find themselves forced to answer to offstage puppet masters.
I believe there's something in the water in DC. Seems like every good person who gets to Washington in time either gets involved in some scandal, or loses their backbone in order to play the Inside-the-Beltway-Game. The simple politics of Washington seem to have a corrupting influence on good people.