Mark Blumenthal provides a reality check:
[T]his event is extremely important with one small but very crucial audience: The members of the House and Senate and the news junkies that surround and advise them. For them this event probably serves as something of a demonstration project for how the health care debate might play out in their own elections later this fall: Will the substance of the discussion help change the tone of the debate or the coverage? Will health reform supporters gain an upper hand in selling whatever plan faces further votes in the House and Senate? As such, the very small live audience is important, I just wouldn't look for a big, overnight polling surge in either direction.