It all started going downhill in 1986, when the "nonpartisan" (actually bipartisan) Commission on Presidential Debates took over sponsorship of the Presidential debates during the general election from the League of Women Voters. The League of Women Voters' policy for all debates is to include all candidates, including those from third parties on all ballots, and the two larger parties didn't want that. With the CPD (whose members are often corporate lobbyists) running the deabates, big corporate donors are more inclined donate to the debates - it's just another quid pro quo, another piece of the lobbying machine. And now, it seems that the CPD's general election debates are setting the tone for the NBC's of the world to further narrow the field - as if the amount of money needed to run a campaign these days weren't enough - during the primary season.

For more on League of Women Voters debate format:
http://www.lwvohio.org/debate.htm

For information on the running of debates, the role of the CPD and the recently formed counter-movement, the Citizens' Debate Council, see
http://www.opendebates.org