Huffington Post: Force or Fringe. United States Social Forum Vs. Tea Party

It's not surprising that the mainstream media is paying little attention to the 15,000-plus community organizers and progressive activists gathered in Detroit, Michigan this week for the second United States Social Forum. After all, the center-left political establishment isn't paying attention either.
Why is it that the Tea Party -- the right-wing edge of the conservative political sphere -- exerts a gravitational pull on the Republican party and the conservative mainstream while the United States Social Forum and the leaders and groups gathered here, who represent the left of the liberal mainstream, are disregarded as marginal and irrelevant -- that is, if they're regarded at all?