Now Mr. Brock is starting a new endeavor built to combat the very sector of journalism that spawned him, with support from the same sorts of people (Democrats) about whom he once wrote so critically.

With more than $2 million in donations from wealthy liberals, Mr. Brock will start a new Internet site this week that he says will monitor the conservative media and correct erroneous assertions in real time.

The site, called Media Matters, was devised as part of a larger media apparatus being built by liberals to combat what they say is the overwhelming influence of conservative commentators like Rush Limbaugh and Bill O'Reilly.

Mr. Brock's project was developed with help from the newly formed Center for American Progress, the policy group headed by John D. Podesta, the former Clinton chief of staff. And Mr. Brock said he hoped it could help provide fodder for fledgling liberal radio talk shows being started across the country, including those of the comedians Al Franken and Janeane Garofalo.

For Mr. Brock, 41, the project is yet another considerable step in his public evolution from conservative muckraker to liberal activist. That evolution began after Mr. Brock began publicly apologizing in the late 1990's for reporting that brutally criticized Anita F. Hill and a report that Arkansas state troopers had helped Bill Clinton procure paramours when he was the governor of Arkansas, the veracity of which he is no longer sure.

Mr. Brock has also said that he knowingly lied in an article he wrote for The American Spectator in 1992 that raised doubts about the credibility of Ms. Hill. The article formed the basis for a later book about Ms. Hill, whose charges of harassment almost derailed Clarence Thomas's appointment to the Supreme Court.

Mr. Brock said he hoped his new project could be as influential as the Media Research Center, a conservative media monitoring group run by L. Brent Bozell III that frequently calls attention to what it calls examples of liberal bias in the news media. Its findings often become subjects for conservative radio and cable talk shows.

Mr. Brock argued that such monitoring groups have helped build the conservative media's influence, in part by making mainstream journalists toe a more conservative line by convincing them that they are liberally biased.

"The right wing in this country has dominated the debate over liberal bias," Mr. Brock said during an interview Friday. "By dominating that debate, my belief is they've moved the media itself to the right and therefore they've moved American politics to the right."

He added, "I wanted to create an institution to combat what they're doing."

Since his conversion to the left, Mr. Brock has argued that he was representative of many in conservative journalism, an assertion some of his former colleagues angrily deny. Still, Mr. Brock said the central thrust of his group would be to closely monitor conservative commentators and journalists and, when they make erroneous or misleading claims, to point them out and set the record straight on the Media Matters Web site ( www.mediamatters.org ).

In Mr. Brock's new K Street offices on Friday morning, a team of nearly a half-dozen researchers, overseen by Katie Barge, who last worked for the opposition research arm of Senator John Edwards's presidential campaign, sat before a bank of computers and televisions in a room that was otherwise dark.

Some of the researchers wore headphones as they scanned episodes of cable news programs stored on digital recording devices, among them "Hannity & Colmes" on Fox News Channel, "Dennis Miller" on CNBC and "Scarborough Country" on MSNBC. Two researchers have been assigned to cover Mr. Limbaugh, whose program they will regularly transcribe.

Mr. Scarborough, a former Republican representative from Florida, said he did not mind being monitored by the site, so long as it stuck to monitoring accuracy and did not grind too hard a political ax.

"Everybody should welcome fact-checkers if guests, or especially hosts, say things that aren't accurate," Mr. Scarborough said.

While Mr. Bozell did not argue with Mr. Brock's assertion that his group opened the door to greater influence for more conservative outlets, he did not agree with his central premise that conservative commentators had made the mainstream media more conservative.

"I don't think we have pushed the mainstream media to the right," Mr. Bozell said. "I think what we have done is to neutralize their credibility, and every survey in the world shows that the public doesn't believe that these reporters are objective."

But, he said, Mr. Brock's new venture would have greater problems than that. "The problem is that David Brock is a certified liar," he said. "He will forever have a credibility problem. One doesn't know what to believe in David Brock."

Mr. Brock's new Democratic friends said they were not worried about it. "Will the right wing try to demonize him and assassinate his character? I'm quite confident that it will," said Mr. Podesta, the former chief of staff for Mr. Clinton. "But I think David has strength because of his facts and his analysis."

Mr. Podesta has loaned office space in the past to Mr. Brock and introduced him to potential donors.

Among Mr. Brock's donors is Leo Hindery Jr., the former cable magnate; Susie Tompkins Buell, who is co-founder of the fashion company Esprit and is close to Senator Hillary Rodham Clinton of New York, and Ms. Buell's husband Mark; and James C. Hormel, a San Francisco philanthropist whose appointment as ambassador to Luxembourg was delayed for a year and a half in the late 1990's by conservative lawmakers protesting what they called his promotion of a "gay lifestyle."

Mr. Brock, who has also spoken with Senator Clinton, Senator Tom Daschle of South Dakota and former Vice President Al Gore about his project, said he was ready to face skepticism. "I think all ideological converts face a reality on that question," he said. But, he added, "I've found people very open to the idea that people can change."

Want to answer my question, since you've been pushing the left's TP talking points on us?

Also, others here (such as Winchester) cite their sources/links (which you typically criticize as biased)--why do you so often not cite your quotes? In this case--a wiki citation--really?