A professional politician focuses on delivering the goods for his campaign contributors. At first he may do this with distaste, but as the years go by and his corruption advances, he does it with gusto and grim relentlessness. On budget issues, he considers neither the good of the country nor the interests of future generations. He is like a drug addict, and special interests pay for his habit; they are his master. He may help other politicians advance their special interests in return for support for his own, but that is the limit of his reasonableness.
By contrast, when a businessman, architect, lawyer, pilot, engineer or some other ordinary citizen takes a sabbatical from his job and sits on the legislature for a year, the narcotic effects of power are unfelt by him and there is nothing the lobbyists can offer him. He reflects, “In my whole life, I have sought to improve the lot of myself and my family. Now here is a chance for me to do some good for my ward/county/state/country.” This was the untainted motive of Jefferson and Madison the plantation owners, Franklin the printer, Adams the lawyer, Washington the soldier, and Paine the bridge engineer.