Potential candidates for the Democratic presidential nomination in 2008 are tripping over one another to tout their support for so-called net neutrality legislation, which would prohibit companies that provide Internet access from giving priority treatment to data, voice, and video streams from preferred content providers.

Senator Clinton sent an e-mail to her supporters yesterday styling herself as a leader in the “fight” to save the Web from business interests that could stifle freewheeling discussion on important issues.

Mrs. Clinton, who for years has been the object of vitriol and vulgarity on Web bulletin boards, hailed the Internet as a “growing, vibrant source of political debate.”

“Preferential treatment could make it harder for individual voices to be heard,” she warned her backers. “Please join me in protecting an Internet where everyone can have a voice.”

Mrs. Clinton’s missive noted that she was an original co-sponsor of a Senate bill to enforce net neutrality, the Internet Freedom Preservation Act.

Last week, a former senator from North Carolina who is considering a presidential bid in 2008, John Edwards, sent a similar message to his followers. “On the Internet, big corporations are on equal footing with everyday people. And it needs to stay that way,” he said.

Echoing themes from his 2004 presidential bid, Mr. Edwards warned darkly of a plan to create two Americas on the Web. “Special interests are pushing bills through Congress that would divide the Internet in two. Corporate deals would determine which Web sites would run incredibly fast and which ones would barely run at all,” he wrote.

A former governor of Virginia and 2008 presidential hopeful, Mark Warner, released a video podcast last month pledging his support for the net neutrality campaign. “We’ve got to keep the Internet free and open, he said. “Make sure that the policy of net neutrality becomes the law of the land.”

The net-neutrality measure has gathered support from a wide range of citizens groups including MoveOn.org, Common Cause, the Gun Owners of America, and the Christian Coalition. However, the energy behind the bill has come primarily from liberal bloggers, often referred to as the netroots.

Netroots activists have heaped derision on a former spokesman for President Clinton, Michael McCurry, who is working as a consultant for telephone and cable companies opposed to the net neutrality legislation. Posters on liberal blogs called him “a stooge,” “a shill,” or worse. “Drop McCurry a note and tell him to crawl back into whatever hole he crawled out of,” a comment on the thoughtcrimes.org Web site said.

Mr. McCurry told The New York Sun yesterday that he believes the activism by potential 2008 candidates is being driven by political considerations. “It’s a way to demonstrate that you hear what the blogosphere cry is all about,” he said. “Regardless of whether it’s good policy or bad policy, it’s certainly a way to put one on the scoreboard for the bloggers.”

Asked about Mrs. Clinton’s blast email drawing attention to her position on the issue, Mr. McCurry said, “I certainly understand Mrs. Clinton doing it. I think it’s bad policy because it won’t build us the Internet we need.”

Mr. McCurry and the phone and cable companies argue that the Internet is already straining under increasing use of video and other applications that use large swaths of bandwidth. The Internet access firms contend that they should be able to pay for upgrades to the Internet backbone by charging movie services and popular sites like eBay and Google for reliable, fast delivery of their data.

Mr. McCurry said fears that providers could cut off access to disfavored sites are unwarranted. “There would be immediate public response that is market damaging,” he said. He also said the Federal Communications Commission is already empowered to act in such cases.

The former White House spokesman pointed out that while some in the netroots rail against him, funding for the campaign in favor of the legislation is also coming from huge companies, such as Google and Yahoo. “Much as they try to turn me into a shill, they have succumbed to the same thing on the other side,” he said.

A spokesman for a nonprofit group organizing support for the net neutrality legislation, Free Press, said there have already been instances where providers have blocked certain e-mail messages or voice-over-Internet phone calls. “If they want to build systems where everyone who wants to send video has to pay, fine, but you have to treat everybody the same, not just the telcos and their corporate partners,” the spokesman, Craig Aaron, said.

In a House vote earlier this month, a net neutrality amendment failed, by 152 to 269. Most Republican lawmakers opposed the legislation, but there were some notable GOP exceptions. The chairman of the House Judiciary Committee, Rep. James Sensenbrenner of Wisconsin, cast a vote in favor of the neutrality language, as did the former chairman of the House Government Reform and Oversight Committee, Rep. Dan Burton of Indiana.

One of the original sponsors of the Senate bill is a Republican, Senator Snowe of Maine.

According to observers on both sides of the debate, the only Democratic Senator to express serious concern in public about the measure is Senator Biden of Delaware, another possible presidential candidate in 2008. At a hearing last week, Mr. Biden said he saw no pressing need for the legislation and suggested that a public outcry would force Congress to act if Internet companies started cutting off access to unpopular sites.

Senator Kerry of Massachusetts, who was the Democratic presidential nominee in 2004 and may try again, is aggressively supporting the net neutrality legislation, a spokesman, David Wade, said.

The creator of the popular liberal blog Dailykos.com, Markos Moulitsas, told the Sun that 2008 contenders are being smart to embrace net neutrality. “Those that pay more than lip service to the issue, but actively work to ensure net neutrality are going to get extra points. This issue won’t make a candidate, but it could certainly break one,” Mr. Moulitsas said in an e-mail.

However, Mr. McCurry said those Democrats who follow the netroots could also pay a price.

“We’re trying to create a cost to being the first to introduce a heavy dose of regulation to the Internet. They’ll have to wear that label, too. It doesn’t make you sound pro-entrepreneurial and it’s not a ‘new Democrat’ message,” he said.