Reuters
A rally and march in protest of higher taxes in Santa Barbara, Calif., April 4.
.So who's behind the Tax Day tea parties? Ordinary folks who are using the power of the Internet to organize. For a number of years, techno-geeks have been organizing "flash crowds" -- groups of people, coordinated by text or cellphone, who converge on a particular location and then do something silly, like the pillow fights that popped up in 50 cities earlier this month. This is part of a general phenomenon dubbed "Smart Mobs" by Howard Rheingold, author of a book by the same title, in which modern communications and social-networking technologies allow quick coordination among large numbers of people who don't know each other.

In the old days, organizing large groups of people required, well, an organization: a political party, a labor union, a church or some other sort of structure. Now people can coordinate themselves.

We saw a bit of this in the 2004 and 2008 presidential campaigns, with things like Howard Dean's use of Meetup, and Barack Obama's use of Facebook. But this was still social-networking in support of an existing organization or campaign. The tea-party protest movement is organizing itself, on its own behalf. Some existing organizations, like Newt Gingrich's American Solutions and FreedomWorks, have gotten involved. But they're involved as followers and facilitators, not leaders. The leaders are appearing on their own, and reaching out to others through blogs, Facebook, chat boards and alternative media.

The protests began with bloggers in Seattle, Wash., who organized a demonstration on Feb. 16. As word of this spread, rallies in Denver and Mesa, Ariz., were quickly organized for the next day. Then came CNBC talker Rick Santelli's Feb. 19 "rant heard round the world" in which he called for a "Chicago tea party" on July Fourth. The tea-party moniker stuck, but angry taxpayers weren't willing to wait until July. Soon, tea-party protests were appearing in one city after another, drawing at first hundreds, and then thousands, to marches in cities from Orlando to Kansas City to Cincinnati.

As word spread, people got interested in picking a common date for nationwide protests, and decided on today, Tax Day, as the date. As I write this, various Web sites tracking tea parties are predicting anywhere between 300 and 500 protests at cities around the world. A Google Map tracking planned events, maintained at the FreedomWorks.org Web site, shows the United States covered by red circles, with new events being added every day.

The movement grew so fast that some bloggers at the Playboy Web site -- apparently unaware that we've entered the 21st century -- suggested that some secret organization must be behind all of this. But, in fact, today's technology means you don't need an organization, secret or otherwise, to get organized. After considerable ridicule, the claim was withdrawn, but that hasn't stopped other media outlets from echoing it.

There's good news and bad news in this phenomenon for establishment politicians. The good news for Republicans is that, while the Republican Party flounders in its response to the Obama presidency and its programs, millions of Americans are getting organized on their own. The bad news is that those Americans, despite their opposition to President Obama's policies, aren't especially friendly to the GOP. When Republican National Committee Chairman Michael Steele asked to speak at the Chicago tea party, his request was politely refused by the organizers: "With regards to stage time, we respectfully must inform Chairman Steele that RNC officials are welcome to participate in the rally itself, but we prefer to limit stage time to those who are not elected officials, both in Government as well as political parties. This is an opportunity for Americans to speak, and elected officials to listen, not the other way around."

Likewise, I spoke to an organizer for the Knoxville tea party who said that no "professional politicians" were going to be allowed to speak, and he made a big point of saying that the protest wasn't an anti-Obama protest, it was an anti-establishment protest. I've heard similar things from tea-party organizers in other cities, too. Though critics will probably try to write the tea parties off as partisan publicity stunts, they're really a post-partisan expression of outrage.

Of course, it won't be the same everywhere. There are no national rules, and organizers of each protest are doing things the way they want. And that's the good news and the bad news for Democrats. It's not a big Republican effort. It's a big popular effort. But a mass movement of ordinary people who don't feel that their voices are being heard doesn't bode well for the party that positioned itself as the organ of hope and change.

Will these flash crowds be a flash in the pan? It's possible that people who demonstrate today will find that experience cathartic enough -- or exhausting enough -- that that will be it. But it's more likely that the tea-party movement will have an impact on the 2010 and 2012 elections, and perhaps beyond.

What's most striking about the tea-party movement is that most of the organizers haven't ever organized, or even participated, in a protest rally before. General disgust has drawn a lot of people off the sidelines and into the political arena, and they are already planning for political action after today.

Cincinnati organizer Mike Wilson, a novice organizer who drew 5,000 people to a rally on March 15, is now planning to create a political action committee and a permanent political organization to press for lower taxes and reduced spending. Tucson tea party organizer Robert Mayer told me that his organization will focus on city council elections in the fall as its next priority. And there's lots of Internet chatter about ways of taking things further after today's protests.

This influx of new energy and new talent is likely to inject new life into small-government politics around the nation. The mainstream Republican Party still seems limp and disorganized. This grassroots effort may revitalize it. Or the tea-party movement may lead to a new third party that may replace the GOP, just as the GOP replaced the fractured and hapless Whigs.

Mr. Reynolds is the author of "An Army of Davids: How Markets and Technology Empower Ordinary People to Beat Big Media, Big Government, and Other Goliaths" (Thomas Nelson, 2006). He will be covering the tea party protests today at PJTV.com.