Via DeLong, Here is an essay by Washington Post reporter Walter Pincus. Much good stuff. The nutshell thesis: Modern journalists have shied away from the necessary and valid role they play in influencing the federal government.
Pincus attributes this phenomenon to the pursuit of objectivity, to the desire to stay above the conflict of ideas. That may go a long way as explanation, but I'd throw in something else.
It seems to me that people are extremely pessimistic about the capability and utility of the federal government. There is a sense that the major social conflicts and tensions such as poverty, race relations, and terrorism cannot be solved or even improved by government. The gospel of Reagan. And if the government is going to get it wrong no matter what, then who cares what it does? Maybe journalists trivialize politics because they cannot imagine it having more then trivial significance.