First of all, Colbert and Stewart are brilliant comedians. They've put together something that speaks to their audience, which is really a large cross section of Americans.
Many of my not-very-political friends really respond to all of this. They are sick and tired of the alarmism and hysteria that dominates the media and American political discourse. I would guess that many of these folks would call themselves "independents." They are upset with the system, but they don't buy the garbage being promoted by both major parties.
I doubt that many people went to today's rally because they agree with Stewart's call for "moderation." Many went for the comedy and the good time. I'll bet that many wanted to show up to stick this thing in Glen Beck's craw. This event should go a long way to marginalize Beck, Limbaugh and their ilk. And I'll bet that many are upset with the current political system, but aren't interested in joining the Tea Party.
My two cents.
Chuck