Why can't third party presidential candidates participate in the debates? Why aren't they covered by national media?

In 2000, I voted for libertarian candidate Harry Browne (look at how many presidential candidates there were in 2000!) because I liked what he had to say. Nowadays, I find myself liking Michael Badnarik, for the most part, but I'm afraid to vote for him because then a candidate I really don't want in office might be elected. The main reason that this is a legitimate concern is not because there's precedent, but because nobody knows or cares about a so-called "third party" candidate. Recent events at the Presidential Debate in St. Louis give us a clue as to why.

These candidates aren't trivial, but they are treated that way by the press and by the structures that currently exist for electing a president. Here's a good (if brief) article from PBS on the subject.

Because I feel that this is totally stupid, I'm going to copy what a Xanga user named Mellifluous posted to her blog this morning.

On October 8th at 9PM, two third party candidates were arrested for attempting to enter the Washington University complex holding the second presidential debate. The candidates, Michael Badnarik of the Libertarian Party and David Cobb of the Green Party, chose civil disobedience to fight the bipartisan Commission on Presidential Debates (CPD). Over half of Americans believe third party candidates should be included, yet politicians continue to funnel public funds into the bi-partisan Commission. S.W.A.T. teams were used to deny the will of the American people while mainstream media ignored this historic event, a shameless suppression of political diversity.

Americans deserve to know about the unjust takeover of our political process. I posted this to take matters into my own hands. If you believe that real democracy thrives on diverse political voices and that it's time to use alternative methods to support these voices, post this in your Xanga, profile, or Livejournal, or e-mail it to those who care.