CULVER CITY, CALIF.: The video blasted across the Internet, drawing political blood from Sen. John McCain within a matter of days.

Produced in a cluttered former motel behind the Sony Pictures lot, it juxtaposed harsh statements about Islam made by the Rev. Rod Parsley with statements from McCain praising Parsley, a conservative evangelical leader. The montage won notice on network newscasts this spring and ultimately helped lead McCain, the likely Republican presidential nominee, to reject Parsley's endorsement.

In previous elections, an attack like that would have come from party operatives, campaign researchers or the professional political hit men who orbit around them.

But in the 2008 race, the first in which campaigns are feeling the full force of the changes wrought by the Web, the most attention-grabbing attacks are increasingly coming from people outside the political world.

In some cases they are amateurs operating with nothing but passion, a computer and a YouTube account, in other cases sophisticated media types with more elaborate resources but no campaign experience.

So it was with the Parsley video, which was the work of film director Robert Greenwald, 64, and his small band of 20-something assistants. Once best known for films like Xanadu and the television movie The Burning Bed, Greenwald shows how technology has dispersed the power to shape campaign narratives, potentially upending the way American presidential campaigns are fought.

Greenwald's McCain videos have been viewed more than 5 million times — more than McCain's own campaign videos have been downloaded on YouTube.

Greenwald said he had no ties to the Democratic party or Sen. Barack Obama's campaign.

Four years ago, the Internet was a Wild West that caused the occasional headache for the campaigns but for the most part remained segregated from them.

This year, the development of cheap new editing programs and fast video distribution through sites like YouTube has broken down the barriers, empowering a new generation of largely unregulated political warriors who can affect the campaign dialogue faster and with more impact than the traditional opposition research shops.

The better-circulated videos have generally come from people with some production experience. One of the most widely seen anti-Obama videos was created by Jason Mitchell, 29, who produces evangelical Christian programming in Durham, N.C.

A conservative-leaning version of YouTube called Eyeblast.tv has recorded millions of hits on the video.

Its announcer notes that Obama's father was Muslim, asserts that the candidate attended a Muslim grammar school in Indonesia for two years, and asks, ''When we are at war with Islamic terrorism, can Americans elect a man with not one, not two, but three Islamic names?'' One on screen image shows Obama's face morphed with that of Osama bin Laden.

Mitchell said he sticks close to the factual record, but the video has been widely criticized as over the line. Obama is a Christian. The school in Indonesia was secular.