American Bridge 21st Century, the super PAC that grew out of David Brock’s media watchdog of the left, has become the opposition research hub of the Democratic fundraising apparatus, following Republican candidates on the trail, rooting around their closets for skeletons and furiously pumping out snarky Web videos. 

Representatives from the group are in communication daily with the top Democratic independent expenditure committees: Priorities USA, Majority PAC and House Majority PAC.

“Our research helps to inform their polling; their polling helps us decide where we want to do our media hits,” said Chris Harris, communications director of American Bridge 21st Century. “Our existence means that they don’t have to put trackers out there and they don’t have to do research.”

Much of the organization’s most effective work goes on behind the scenes, as it quietly feeds material to reporters all over the country.

In August, Bridge videographers caught Nebraska Senate candidate and Attorney General Jon Bruning comparing welfare recipients to raccoons. The film yielded 26 news stories.

In October, the group’s researchers noticed that Sen. Scott Brown (R-Mass.) had lifted a passage verbatim from a speech given by former Sen. Elizabeth Dole (R-N.C.). At least 40 news outlets produced original pieces based on the tip, including an Associated Press story published in more than 140 newspapers and websites, according to the organization’s internal performance measurements.

American Bridge 21st Century raised $3.7 million from fewer than 50 individual donors and unions last year, federal records show, drawing on the strategies and supporters cultivated at Media Matters for America, an organization that Brock founded in 2004 to counter what the group calls  conservative misinformation.

The group’s sister nonprofit arm, American Bridge 21st Century Foundation, which is not required to disclose its donors, raised an additional $2.7 million last year. The foundation then transferred nearly $223,000 of that untraceable money to the super PAC, a controversial move that has raised concerns among campaign finance reform advocates. Harris said the payment was a reimbursement for shared staff, office space and equipment such as computers and printers, not an attempt to move program money around.

Brock, a conservative-journalist-turned-Democratic-activist, presides over a network of fundraising entities that includes two political nonprofits, the political action committee and a nonprofit tied to Media Matters that is barred from political activity.

“The long-term plan was always to have Media Matters occupy all of the spaces it could occupy,” one former employee said. “They try to create their own echo chamber. It’s a fabulous strategy.”

But interviews with former Media Matters employees reveal a picture of a sprawling and paranoid organization that has at times grappled with frequent turnover and disgruntled employees. They describe Brock, a well-respected operative and prolific fundraiser, as a shy, even shadowy, manager.

“Somehow he can get these billionaires to part with large sums of money,” another former senior employee said. “Yet, he was just terrible at dealing with the people who work with him.”

Media Matters and American Bridge rely on many of the same donors — such as Peter Lewis, the billionaire chairman of Progressive Insurance who gave $200,000 to the Bridge super PAC  last year and has supported Media Matters in the past — and share the same fundraising firm, the Bonner Group.

It is not clear whether Brock’s commitment to building a powerful super PAC this cycle has detracted from Media Matters.

Financial information is not available for 2011, but Ari Rabin-Havt, executive vice president of Media Matters, said the group has not suffered because of the growth of American Bridge. Media Matters raised $13.2 million in 2010, up from $6.7 million the year before, according to the most recent IRS filings.

“Bridge has more of a focus on this year’s election cycle,” one donor who has supported both organizations told Roll Call. “There will be all this super PAC money, and most of it coming from the right. The left needs to defend itself.”

Even though Republican super PACs outraised Democratic groups 3-to-1 in 2011, Democrats say that for the first time, they are poised to win the messaging war.

“I rely on [Bridge] everyday,” said Paul Begala, a consultant and strategist for Priorities USA. “The duplication of effort that would be required if Bridge did not exist would be massive and expensive.”

The right does not have anything like it — a PAC serving as a clearinghouse for opposition research. And while liberals rail against the Supreme Court decision that ushered in this new breed of PAC that can accept unlimited donations from corporations and individuals, they agree that the existence of super PACs facilitates coordination between third-party groups.

American Crossroads, the leading GOP super PAC that focuses almost entirely on paid media, has fewer than 20 staffers compared with Bridge’s 50 employees.

Bridge has run only one paid advertisement, a print spread funded by the organization’s 501(c)(4) arm dinging former Massachusetts Gov. Mitt Romney for changing his stance on abortion.

“It’s a very different model than Crossroads,” said Jonathan Collegio, communications director of American Crossroads. “They have an extremely high overhead and burn rate because there is so many staff.”