Kevin Drumm at Mother Jones sums things up:
It just costs too much to run for Congress today for anyone who’s not fairly well off to do it. And that’s no coincidence. As income inequality goes up, campaign funding from rich donors also goes up — partly because the rich have more money and partly because they’re more motivated to use that money to influence the political process in order to protect their wealth. This creates an arms race that effectively precludes anyone who doesn’t have either money of their own or access to wealthy donors from running. And that means that Congress has fewer and fewer members with any real connection to the working world. Is it any wonder that members of Congress these days don’t really care at all about the views of the poor and the working class?