Eventually, Mr. Marshall decided to postpone the book project. Instead of focusing on other people’s explorations, he would forge ahead with his own. In the fall of 2004, the trailblazing, almost neurotically obsessive reporter behind the Talking Points Memo Web site set off into the next unsettled realm of 21st-century media: Web TV.

He’s still very much in the testing phase.

On a drizzly day in mid-May, Mr. Marshall stood on a sidewalk in midtown Manhattan and began filming a short piece for his Web site. A man holding a garbage bag strolled behind him. A loud clanking sound came from somewhere off camera. A car honked. Somebody began dismantling the awning under which Mr. Marshall stood. “It’s a perfectly nasty day here in New York City,” Mr. Marshall told the camera. “I’m kind of under the gun here.” And then: “This isn’t working.”

Afterward, Mr. Marshall finished shooting indoors. Later, when he posted the piece on his Web site, he didn’t bother to edit out the flubs.

“Each time we do something that is outside of our core thing, we ask ourselves, ‘What is it that our audience likes about us?’” he told The Observer in a recent interview in TPM Media headquarters, on the third floor of a small building above a bustling plant shop in midtown Manhattan. “With text, there’s an intimacy to the writing that I think our readers really key into. We want to have decent production values, but we want to preserve that feeling with video.”

Mr. Marshall was dressed in jeans and a dress shirt. His sleeves were rolled up. Empty Starbucks cups littered his desk.

Things were busy. For the next hour, Mr. Marshall tried to ignore his phone, which rang constantly, and the questions from his staff, which were persistent, and an invitation to speak at a major university, which was up in the air, long enough to spell out his philosophy on Web video.

For the past several months, he has been filming a show called TPM TV, which appears on his site four days a week. Mr. Marshall said that he was still figuring out what makes for must-see Web TV.

In recent weeks, he has taped two dispatches from a politics and new media conference at Pace University. He has interviewed Al Franken. And he has filmed analytic episodes in which he has attempted to compile a series of piecemeal blog posts into a fully formed narrative.

“We want to find a way to take the most important things we’re working on and package them in what we think is an inherently accessible medium in both a technological and conceptual sense,” said Mr. Marshall. “If it goes viral, the aim is, a person who doesn’t know what we’ve been doing can see it and it makes sense.”

“Hopefully we can reach a much larger potential audience,” he added.

Mr. Marshall has already built up a considerable following—he says the suite of sites gets 400,000 page views a day—on the strength of a reputation built on periodic, spectacular reporting coups. In December 2002, he drove national attention to racially charged remarks by Trent Lott that eventually led to his resignation as Senate Majority Leader. In 2004 and 2005, Mr. Marshall’s relentless advocacy reporting forced members of Congress to take specific positions on the privatization of Social Security—which, in turn, eventually helped to sink the President’s Social Security plans. This year, he has been the driving force behind the media’s coverage of the fired U.S. Attorneys, and the subsequent pressure on Attorney General Alberto Gonzalez to step down.

In a few weeks, Talking Points Memo will put its increasing reliance on Web video—and its entire business model—to the test, when it undergoes its most radical redesign since Mr. Marshall created the site nearly seven years ago. Mr. Marshall said that the new layout, which will debut sometime in July, will feature more aggregated daily news and a more TV-friendly format.

According to Mr. Marshall, the content on the new site will be nearly twice as wide. The blog will occupy the left side of the page. The right side will provide coverage of the news of the day, including articles from wires services, original stories from Mr. Marshall’s growing news staff (he’s now up to six full-time employees) and links to stories from other publications.

The newly revamped site will also serve as an improved portal to the accompanying TPM satellite sites: the online salon TPMCafe, the investigative-reporting blog TPMmuckraker and a frequently updated politics blog called TPM Election Central.

And of course, on the new site, TPM TV will have a permanent, prominent home near the top of the page.

“The basic idea is that we’ve been evolving from being one blog to being a full-service news site for politics and serious national news,” said Mr. Marshall. “We want our readers to know that if they don’t see it on our site, it hasn’t happened yet.”

Mr. Marshall declined to discuss how much revenue the TPM franchise is currently generating, other than to say that it’s “enough to pay for six full-time staff members.” He said that he was investing a “few tens of thousands of dollars” in the redesign.

Whether the newfangled site ultimately succeeds will depend in part on Mr. Marshall’s ability to transform himself from a rumpled, bespectacled link jockey with a monitor tan into a viable Web TV anchor. That might seem like an odd gamble for a guy whose past accomplishments—he earned a Ph.D. in American history at Brown University, wrote for the likes of The Atlantic Monthly and The New Yorker, and created what has been by almost any measure one of the most successful political blogs since the form was invented—have depended on his way with the written word.

But Internet activists say that such transformations are no longer optional.

Andrew Rasiej, the former nightclub owner and founder of Personal Democracy Forum who has become something of an Internet prophet, was one of the people who advised Mr. Marshall about the necessity of getting into video content.

“There’s an inherent danger in not recognizing that the Internet is becoming much more video-based than text-based,” said Mr. Rasiej. “The new skill set that’s going to be required is ‘videracy,’ not just literacy. Bloggers who fail to understand the shifting dynamic do so at their own peril.”

Mr. Rasiej has faith that Mr. Marshall will succeed in the new medium. “Josh has already proven that he can build an audience online and that he doesn’t need the banner of The Washington Post or The New York Times above his name,” said Mr. Rasiej. “He is about to prove that the same is true in Internet video, where he doesn’t need CNN or PBS or MSNBC to get the eyeballs and the traffic necessary to build an audience.”

Jeff Jarvis, the founder of new media blog BuzzMachine.com, also thinks that Mr. Marshall is making a wise investment. “We’re all experimenting,” said Mr. Jarvis. “It’s a great time to be doing this. Web video is going to be critical to this world.”

Some more traditional journalists seem somewhat less certain. Nicholas Lemann, the dean of the Columbia Journalism School and the author of The New Yorker’s Wayward Press column, pointed out that Web video, like the Internet itself, is still in its infancy.

“It’s very, very early,” said Mr. Lemann. “The Web is miraculously large in its capabilities. It isn’t clear to me what kind of medium it will end up being when the dust settles 20 years from now.”

“If you said, simply, what’s in the ascendancy: traditional start-to-finish texts or visual, I’d say that visual is gaining ground faster than text at this moment,” said Mr. Lemann. “But I also think that whole other things we don’t see yet could wind up happening on the Web. So I don’t want to say ‘game over, video has won.’”

Mr. Marshall, for his part, said he felt at ease making the transition. “It’s not that I feel any immediate sense of being overtaken,” he said. “But the technology does move quickly. I’ve thought for about two years that video was a key thing that we needed to do much more of. So part of it is just keeping up with the evolution of the medium.”

In addition to the regular broadcasts of TPM TV, Mr. Marshall said that in the coming months he will be integrating more video clips from traditional news TV shows into the TPM blog. To this end, Mr. Marshall has outfitted TPM with a system that continuously records all of the major cable television news networks, plus one floating channel. Every two days, the footage loops back over itself like a security camera.

“One of the things that we’re trying to leverage is that we have this audience who write in and say, ‘Oh my god, this is what I saw,’” said Mr. Marshall. “As long as they get to us within a day or so, we can go back and get it.”

Recently, Mr. Marshall filmed a segment of TPM TV in which he encouraged his readers to hit the campaign trail with digital-video cameras. On the new site, there will be a place for users to easily upload their resulting footage.

“We’re not just looking for ‘Macaca’ moments,” said Mr. Marshall, referring to the damaging video snippet of a speech by former Senator George Allen of Virginia that upended his re-election campaign. “We’d love to have that. But it’s not principally what we’re looking for. We’re looking to get a more vérité sense of the day-to-day campaign trail.”

Mr. Marshall leaned back in his chair. Behind him, a digital camera peeked out from the top of his desktop computer. For a while, Mr. Marshall was shooting many of the early TPM TV episodes using the monitor-mounted camera. In those episodes, an orange lava lamp can be seen resting conspicuously in the background. Mr. Marshall has since switched to a different spot in the office for filming. Now he typically stands in front of a row of wall-mounted flat-screen televisions. The lava lamp is nowhere to be seen.

“There’s no logic to it,” said Mr. Marshall. “We’re just experimenting.”