Sen. John McCain complains -- sometimes jokingly and sometimes seriously -- that there is a liberal bias in reporting that works to his detriment. This perception also shows up repeatedly in letters to the editors of papers across the country, and in the blogosphere.

Surveys and donor lists do show that the majority of both print and on air reporters are liberal. There is less evidence that their liberal leanings affect their reporting. The fact that the overwhelming numbers of owners of newspapers, TV stations and networks are conservative (ironically not a problem for those who complain about bias) would seem to provide a built-in bias suppressor.

The perception of bias may have more to do with the reader's own world-view than with the objective facts. More than any other profession, reporters have to determine what is really going on in the world and how it affects people's lives. They need a historical sense and knowledge of the wider world to put things in context. Their job is to dig for the facts, not opinions.

What could explain why the majority of those who know most about the real world support liberal causes and candidates? It might just be because they have learned that those programs and candidates are more likely to make the world a little more just and a little easier for the most people.