Wayne Madsen Report explains:
"Very few Democratic members of Congress to appear. Reason: [leading pro-Israel lobbyists] The American Israel Public Affairs Committee (AIPAC), according to Democratic insiders on Capitol Hill, put out the word that any member of Congress who appeared at the protest, where some speakers were to represent pro-Palestinian views, would face the political wrath of AIPAC.
"According to Democratic sources on the Hill, Rep. Barney Frank of Massachusetts was the chief conveyor of the AIPAC warning to his colleagues. At the time of this report, three members of Congress were to address the anti-war protestors: Reps. Cynthia McKinney (D-GA), John Conyers (D-MI), and Lynn Woolsey (D-CA). The word is that AIPAC will direct its massive campaign support to Woolsey's neo-con and pro-Iraq war primary challenger, California State Assemblyman Joe Nation, who has strong connections to the Rand Corporation, one of the Pentagon's chief war-making think tanks. Woolsey represents California's Marin and Sonoma counties."