Democrats and Republicans are sharply increasing their use of e-mail, interactive Web sites, candidate and party blogs, and text-messaging to raise money, organize get-out-the-vote efforts and assemble crowds for a rallies. The Internet, they said, appears to be far more efficient, and less costly, than the traditional tools of politics, notably door knocking and telephone banks.

Analysts say the campaign television advertisement, already diminishing in influence with the proliferation of cable stations, faces new challenges as campaigns experiment with technology that allows direct messaging to more specific audiences, and through unconventional means.

Those include Podcasts featuring a daily downloaded message from a candidate and so-called viral attack videos, designed to trigger peer-to-peer distribution by e-mail chains, without being associated with any candidate or campaign. Campaigns are now studying popular Internet social networks, like Friendster and Facebook, as ways to reaching groups of potential supporters with similar political views or cultural interests.

President Bush's media consultant, Mark McKinnon, said television advertising, while still critical to campaigns, had become markedly less influential in persuading voters that it was even two years ago.

"I feel like a woolly mammoth," Mr. McKinnon said.

What the parties and the candidates are undergoing now is in many ways similar to what has happened in other sectors of the nation — including the music industry, newspapers and retailing — as they try to adjust to, and take advantage of, the Internet as its influence spreads across American society. To a considerable extent, they are responding to, and playing catch up with, bloggers who have demonstrated the power of their forums to harness the energy on both sides of the ideological divide.

Certainly, the Internet was a significant factor in 2004, particularly with the early success in fund-raising and organizing by Howard Dean, a Democratic presidential contender. But officials in both parties say the extent to which the parties have now recognized and rely on the Internet has increased at a staggering rate over the past two years.

The percentage of Americans who went online for election news jumped from 13 percent in the 2002 election cycle to 29 percent in 2004, according to a survey by the Pew Research Center after the last presidential election. A Pew survey released earlier this month found that 50 million Americans go to the Internet for news every day, up from 27 million people in March 2002, a reflection of the fact that the Internet is now available to 70 percent of Americans.

This means, aides said, rethinking every assumption about running a campaign: how to reach different segments of voters, how to get voters to the polls, how to raise money, and the best way to have a candidate interact with the public. In 2004, John Edwards, a former Democratic senator from North Carolina and his party's vice presidential candidate, spent much of his time talking to voters in living rooms in New Hampshire and Iowa; now he is putting aside hours every week to videotape responses to videotaped questions, the entire exchange posted on his blog.

"The effect of the Internet on politics will be every bit as transformational as television was," said Ken Mehlman, the Republican national chairman. "If you want to get your message out, the old way of paying someone to make a TV ad is insufficient: You need your message out through the Internet, through e-mail, through talk radio."

Michael Cornfield, a political science professor at George Washington University who studies politics and the Internet, said campaigns were actually late in coming to the game. "Politicians are having a hard time reconciling themselves to a medium where they can't control the message," Professor Cornfield said. "Politics is lagging, but politics is not going to be immune to the digital revolution."

If there was any resistance, it is rapidly melting away.

Mark Warner, the former Democratic governor of Virginia, began preparing for a potential 2008 presidential campaign by hiring a blogging pioneer, Jerome Armstrong, a noteworthy addition to the usual first-wave of presidential campaign hiring of political consultants and fund-raisers.

Mr. Warner is now one of at least three potential presidential candidates — the others are the party's 2004 presidential and vice presidential candidates, Senator John Kerry of Massachusetts and Mr. Edwards — who are routinely posting what aides say are their own writings on campaign blogs or on public blogs like the Daily Kos, the nation's largest.

Analysts said that the Internet appeared to be a particularly potent way to appeal to new, young voters, a subject of particular interest to both parties in these politically turbulent times. In the 2004 campaign, 80 percent of people between the age of 18 and 34 who contributed to Mr. Kerry's campaign made their contribution online, Carol Darr, director of the Institute for Politics, Democracy and the Internet at George Washington University.

Not incidentally, as it becomes more integrated in American politics, the Internet is being pressed into service for the less seemly side of campaigns.

Both parties have set up Web sites to discredit opponents. In Tennessee, Republicans spotlighted what they described as the lavish spending habits of Representative Harold E. Ford Jr. with a site called www.fancyford.com. That site drew 100,000 hits the first weekend, and extensive coverage in the mainstream Tennessee press, which is typically the real goal of creating sites like this. And this weekend, the Republicans launched a new attack site, www.bobsbaggage.com, that is aimed at Senator Robert Menendez of New Jersey and focused on ethics accusations against him.

For their part, Democrats have set up decoy Web sites to post documents with damaging information about Republicans. They described this means of distribution as far more efficient than the more traditional slip of a document to a newspaper reporter.

A senior party official, who was granted anonymity in exchange for describing a clandestine effort, said the party created a now-defunct site called D.C. Inside Scoop to, among other things, distribute a document written by Senator Mel Martinez, Republican of Florida, discussing the political benefits of the Terri Schiavo case. A second such site, http://capitolbuzz.blogspot.com, spread more mischievous information: the purported sighting of Senator Rick Santorum, a Pennsylvania Republican, parking in a spot reserved for the handicapped.

On the left in particular, bloggers have emerged as something of a police force guarding against disloyalty among Democrats, as Steve Elmendorf, a Democratic consultant, learned after he told The Washington Post that bloggers and online donors "are not representative of the majority you need to win elections."

A Daily Kos blogger wrote: "Not one dime, ladies and gentlemen, to anything connected with Steve Elmendorf. Anyone stupid enough to actually give a quote like that deserves to have every single one of his funding sources dry up." Asked about the episode, Mr. Elmendorf insisted the posting had not hurt his business, but added contritely: "Since I got attacked on them, I read blogs a lot more and I find them very useful." One of the big challenges to the campaigns is not only adjusting to the changes of the past two years but also to anticipate now the kind of technological changes that might be on hand by the next presidential campaign. Among those most cited are the ability of campaigns to beam video campaign advertisements to cell phones.

"All these consultants are still trying to make sense of what blogs are, and I think by 2008 they are going to have a pretty good idea: They are going to be like, 'We're hot and we're hip and we're bloggin',' " said Markos Moulitsas, the founder of the Daily Kos. "But by 2008, the blogs are going to be so institutionalized, it's not going to be funny."

Bloggers, for all the benefits they might bring to both parties, have proved to be a complicating political influence for Democrats. They have tugged the party consistently to the left, particularly on issues like the war, and have been openly critical of such moderate Democrats as Senator Joseph I. Lieberman of Connecticut.

Still, Democrats have been particularly enthusiastic about the potential of this technology to get the party back on track, with many Democratic leaders arguing that the Internet is today for Democrats what talk radio was for Republicans 10 years ago. "This new media becomes much more important to us because conservatives have been more dominant in traditional media," said Simon Rosenberg, the president of the centrist New Democratic Network. "This stuff becomes really critical for us."

For all the attention being paid to Internet technology, there remain definite limitations to its reach. Internet use declines markedly among Americans over 65, who tend to be the nation's most reliable voters. Until recently, it tended to be more heavily used by middle- and upper-income people.

And while the Internet is efficient at reaching supporters, who tend to visit and linger at political sites, it has proved to be much less effective at swaying voters who are not interested in politics. "The holy grail that everybody is looking for right now is how can you use the Internet for persuasion," Mr. Armstrong, the Warner campaign Internet adviser, said.

In this age of multitasking, voters are not as captive to a Web site as they might be to a 30-second television advertisement, or a campaign mailing. That was a critical lesson of the collapse of Mr. Dean's presidential campaign, after he initially enjoyed great Internet success in raising money and drawing crowds.

"It's very easy to look at something and just click delete," said Carl Forti, a spokesman for the National Republican Congressional Committee. "At least if they are taking out a piece of mail, you know they are taking it out and looking at it on the way to the garbage can."