The U.S. Corpgress
Money_003 Stack of corporate money for Congress
(image by Barta IV)
We have the best Congress money can buy.
The worst Congress money can buy.
---Bill Moyers & Michael Winship 
Corpgress is what the money gets.
Congress ought to be called "Corpgress." Corporations, their trade associations, and allies like the U.S. Chamber of Commerce have bought members of Congress lock stock and barrel by financing their election campaigns, by lobbying them for favors, by ghost writing their legislation, and by showering them through loopholes with perks. Nowhere is this truer than when it comes to the war and spy industries that dominate the "corpocracy," or the Devil's marriage between corporations and government. 
The powerless voices for the common good of America are ignored. Congress, through its decisions and actions betray the very idea of public service for the common good. And the American people know it. Congress' reputation has continued to nosedive, with only 10-15% of the populace currently approving its conduct. The American people, except for those in the 10-15% (probably all "members" of the corpocracy) have come to expect nothing good from Congress. How this pathetic and perilous state of affairs has come to pass is no mystery.
The Campaign Trail to the Chambers of Ill Repute
To get elected and reelected to Congress is a very costly pursuit, and the candidates with the most money invariably win. So campaign financing is the key to the office. That is hardly a secret (although the givers and takers would like to keep it a secret).
Politicians campaign for office by tacitly promising once in office to favor wealthy self-interest groups that richly finance their campaigns. Does the thought of "bribery" enter your mind? If you follow the money trail as the authors of The People's Business have, you will see, they say, that a "pattern of influence will inevitably emerge" when major votes on issues affecting particular industries are compared to the campaign money and follow-up lobbying by those industries. 
How could this pattern not emerge? Would any sane person think corporations finance campaigns as a way to strengthen democracy and not themselves? If there were no issues, no huge profits, and no political careers at stake, you can take money to the bank there would be much less money for corporations and their lobbyists and much less job security for politicians.
An indirect benefit to corporations incidentally, is that donations to politicians, particularly to the political careerists (and who in Congress isn't?), buoy share price by giving comfort and assurance to shareholders of politically favored corporations.