This cartoon from The Seattle Times illustrates how America's economic pizza is actually sliced per capita, highlighting the massive disparity between the Top 1%, the merely wealthy, the upper middle class, and the lower 50%.
During the Reagan era, lobbyists were allowed back into Washington, and officials on both sides (or non-partisan) were quickly captured.
Paul Krugman has a great comment about it. Paraphrased, politicians tend to listen more to well-dressed, well spoken lobbyists than they do nerdy economists.