It's an epic brawl between the heaviest of heavyweights. As in 1945, when Harry S. Truman first proposed a national health-care system, the battle is on between a Democratic White House that wants changes, and conservatives and health-care industries that oppose them.

What's new is that much of this slam-bang is being waged, body blow by body blow, on the Web. The opposition has launched a "viral" campaign, culturing on the Internet, then inoculating mainstream media. The tech-savvy White House, after blinking for a few weeks and watching this viral movement take on a life of its own, has mobilized a massive Web counterattack.

This is the Summer of the Raucous Town-Hall Meeting, now a staple of nightly news: crowds jostle, fists shake, voices spar, protesters strap on pistols (as William Kostnic did in Portsmouth, N.H., before an Obama town hall), unaffiliated attendees get roughed up.

At a June 30 health-care meeting with Republican Sen. Mike Castle in Georgetown, Del., a lady in red waved her birth certificate, questioned President Obama's nationality, and insisted on an impromptu Pledge of Allegiance. At Tuesday's meeting in Lebanon, Pa., an irate questioner told Democratic Sen. Arlen Specter that "one day God's going to stand before you and judge you."

Many of these images originated from amateur or cell-phone videos. Clips were then "viralized" - shot instantly throughout the Web at a keystroke. From there, the virus "skipped" into mainstream media, and voila - the story of the summer.

Behold the viral campaign: impossible to stop, fiendishly hard to answer, a blizzard of outrage, ridicule, and bad press.

G. Terry Madonna, director of the Center for Politics and Public Affairs at Franklin and Marshall College, says "the Internet has profoundly affected campaigning, and certainly public-policy deliberations. It provides a way to circumvent the usual media for information delivery."

It's also a study in how all media today, unusual and usual, are interconnected. Talk radio and talk TV are key to the success of any viral campaign. That's why Eric Boehlert, senior editor at liberal advocacy site MediaMatters.org and author of Bloggers on the Bus, says "Fox TV and talk radio are still the main drivers for the conservative movement."

First, the viral videos "skipped" to cable news. Then, as in the "tea party" antitax protests in April, Fox News covered 24/7 what its reporters called a spontaneous national uprising. All major broadcasters picked it up.

Talk-show hosts such as Sean Hannity and Rush Limbaugh publicize town-hall meetings and encourage protest (and conspiracy theories). During his health-care special on Tuesday, Fox opinionator Glenn Beck stood in front of his famed chalkboard and drew links among universal health care, the green movement, forced abortion, and forced sterilization.

Sprouting like mushrooms in the mulch of democracy, a host of Web sites are encouraging protests. Sites such as Townhall.com list meetings and school would-be demonstrators in the fine art of conspicuous dissent.

Former House Majority Leader Dick Armey's site, FreedomWorks; oil billionaire David H. Koch's Americans for Prosperity; and others, such as Grassfire, Tea Party Patriots, and Resistnet, organize objectors and give tips on how to pressure legislators. FreedomWorks, for example, is mailing out 380,000 "August Recess Action Kits" to help the outraged keep up the heat.

The result is what Ross Baker, a professor of political science at Rutgers University, calls "designer indignation." Boehlert agrees: "These town hall meetings are just 'tea parties' indoors." Many of the protestors who enlivened Specter's Lebanon meeting - which Beck later called "wonderful" - told reporters they had been alerted by e-mails from conservative groups such as the Constitutional Organization of Liberty and the Berks County Tea Party.

All of which has created the impression of an angry, coast-to-coast debate. Impression is the operative word. Specter said the angry demonstrators do not "represent all of America." But they don't have to. Small advocacy groups are great at creating sound bites and headlines.

Viral messages also have two magic qualities: They are impervious to correction and they live forever. In an Aug. 7 note on the social-networking site Facebook, now-private citizen Sarah Palin accused the Obama plan of backing a "death panel" that could withhold Medicare money from the elderly and disabled if funds ran low, in effect forcing them to die.

Despite the fact that independent fact-checking Web sites have devastated this claim (Factcheck.org calls it "nonsense," and PolitiFact.com calls it a "sci-fi scenario not based in reality"), the death-panel allegation not only survives, but thrives.

On Aug. 9, Newt Gingrich was on ABC's This Week With George Stephanopoulos supporting Palin: "You're asking us to trust turning power over to the government, when there clearly are people in America who believe in establishing euthanasia . . ."

In a viral campaign, content need not be true, it simply has to resonate. "As with any good conspiracy theory," Boehlert says, "facts never get in the way."

This week, the White House struck back, unleashing its massive Web apparatus. In the Obama administration, the viral warriors face the most Internet-savvy Oval Office ever.

The Obama campaign applied community-organizing principles to the Internet in the 2008 election, resulting in a Web-based community of unprecedented size, flexibility, and responsiveness. That community is still in place. Organizing for America (OFA), Obama's political organization, sent out e-mails and Web posts Sunday urging supporters to stand up for changes to health care at their local town-hall meetings.

OFA reportedly has 13 million-plus names on its mailing list.

On Monday, the White House rolled out Health Insurance Reform Reality Check to rebut objections. Based on the "Fight the Smears" site used to great effect during the 2008 campaign, Reality Check counters each opposition talking point with a video clip. Spokespeople say "health reform will stop 'rationing' - not increase it," or debunk "the malicious myth that reform would encourage or even require euthanasia for seniors." Point by point, Internet-smart, easy to viralize.

Is the viral war having any effect? "I doubt legislators in Washington are much affected," says Baker. "They see it for what it is - not a spontaneous outpouring, but orchestrated by very sophisticated means.

"This has, however, hit Blue Dog Democrats targeted in places where it's possible to rally crowds of angry conservatives."

It's hard to measure how many people viral campaigns reach. Boehlert says "about 20 percent" of the media bump for or against health care is Web-based. Baker thinks "it rallies the passionate faithful but doesn't change many minds."

But who's got the momentum? When the Senate could not pass a bill before the August recess, it was seen as a blow to Obama, who is now on the road - New Hampshire, Montana, Colorado - trying to silence "rumors" that he wants to "pull the plug on Grandma." He is doing so in part because of the Web war.

It may take until September, when Congress reconvenes, to gauge the true impact of that war. But this summer is seeing, as Boehlert puts it, "a theater production that has been building since the spring."

At stake: hundreds of billions of dollars, and health care affecting hundreds of millions of lives. The toe-to-toe slugfest continues, and none of the scorecards is in.