Says Leslie Wayne in the NY Times political blog The Caucus:

Mark your calendar for Sunday night. That’s when Free and Equal.Org, a group formed to encourage third-party candidacies, is promoting a debate at the Columbia Political Union at Columbia University in New York for all six candidates seeking the presidency. The group is pretty much resigned to the fact that neither Senator John McCain nor Senator Barack Obama will be there.

But, others will show, they say. Amy Goodman, principal host of “Democracy Now!” a program of the left-leaning Pacifica radio, will host the event. C-SPAN will also be there to record it….

Just exactly who will be there is still murky…. Ralph Nader, who is on the ballot in 45 states as an independent candidate, has indicated he will show up. Cynthia McKinney, former member of Congress from Georgia and the Green Party candidate, will also be there, according to her website. Ms. McKinney is on the ballot in 30 states. Also invited is Chuck Baldwin, running on the Constitution Party ticket in 35 states…, [who] has gained the endorsement of Ron Paul, whose bid for the Republican nomination garnered a loyal and enthusiastic following.

The only question mark is Bob Barr, the Libertarian Party candidate. Mr. Barr has made it clear that he will only debate Mr. Nader and no one else….