Organizers said the tea party was a grassroots operation made up of average Minnesotans who linked up through the Internet and a few web sites.

But before the event, a spokeswoman for a liberal advocacy group charged that the rally was an "AstroTurf" event, that is, a fake grassroots affair, that was organized by "big corporations or lobbyists for big corporations." Denise Cardinal, executive director of the Alliance for a Better Minnesota, said that while she expected grassroots conservative activists to attend the rally, "the whole synthesis of this event comes from D.C.-based lobbyists."

Cardinal cited a Web site, SaveTheRich.com, that alleged three conservative, lobbyist-run think tanks provided the logistical and public relations support needed to plan the coast-to-coast protests.

First proposed by CNBC's Rick Santelli, the tea parties were promoted by some Fox News hosts.

Cardinal also said many tea party organizers were local Republican Party activists. But the speakers were as critical of Republican officeholders as Democrats for high taxes and wasteful spending.