A new super PAC is calling on congressional candidates to reject outside spending on their behalf by groups financed by secret donors, the latest example of activists embracing a big-money vehicle to fight big money in elections.

CounterPAC is running full-page newspaper ads in Atlanta, Anchorage and Charleston, W.Va., as part of a campaign to pressure candidates to reject spending by groups with murky sources of funding. The super PAC says it will “act as the arbiter and enforcer of the pledge,” which is modeled after a similar agreement between Elizabeth Warren and Scott Brown in the 2012 Massachusetts Senate race to reject outside spending on their behalf.

Candidates who sign the CounterPAC Pledge must give 50 percent of any money spent on their behalf by a group with undisclosed donors to a charity of their opponent's choice.

The group’s first targets are Michelle Nunn (D) and David Perdue (R), candidates in Georgia's Senate race; Sen. Mark Begich (D-Alaska) and likely challenger Dan Sullivan (R); and Rep. Nick Rahall (D-W.Va.) and challenger Evan Jenkins. The super PAC, whose plans were first reported by CNN, plans to jump into other races if its pledge gains traction.

"This is an experiment," said Jim Greer, the former chief executive of the online gaming site Kongregate, who co-founded CounterPAC with Zack Booth Simpson, a research fellow at the University of Texas Center for Systems and Synthetic Biology.

Greer said he was inspired in part by his work as a computer game developer.

"You’ve got all these aggressive teenagers out there trying to break the rules, so you try to incentivize the game so it's fair and fun for everyone," Greer said. As he and Simpson discussed campaign finance issues, "We got to thinking, 'What could you do that it is a private mechanism that would encourage good behavior?'" he recalled.

They decided to focus on groups fueled by secret sources of money.

"That’s something that I think really people from across the political spectrum can honestly agree is corrosive and really indefensible," Greer said.

Such organizations, including Americans for Prosperity and Crossroads GPS on the right and Patriot Majority on the left, have been major players in this year's midterms.

The launch of CounterPAC comes as several other super PACs are working to tamp down the influence of wealthy interests on campaigns. Mayday PAC, which was started by Harvard law professor Lawrence Lessig this spring, has amassed an arsenal of $12 million that it plans to use to bolster five congressional candidates who have committed to backing measures that elevate small donors. Another super PAC, Friends of Democracy, which ran a similar effort in 2012, is rebranding itself as Every Voice Action and expanding its efforts in the states.

The boomlet in anti-big-money super PACs comes as Democrats have sought to make the influence of wealthy individuals on politics a prominent issue in this year’s elections. While the issue animates the liberal base, it remains to be seen how the new groups will demonstrate their impact amid a deluge of political spending.

Like Mayday PAC, CounterPAC is backed by a group of tech entrepreneurs who have not been big political players in the past. Along with Greer, its supporters include Matt Cutts, the head of the Webspam team at Google; Ethan Beard, an entrepreneur-in-residence at Greylock Partners; Ted Wang, a Silicon Valley lawyer; Roy Bahat, head of a new venture fund backed by Bloomberg L.P.; Todd DiPaola, co-founder of InMarket; and Ron Carmel, co-founder of 2D Boy and IndieFund.

"You’re in the middle stages of life and you want to have impact on something outside of just tech," said Greer, adding that CounterPAC has raised more than $1 million, with commitments of more down the road if it is effective.

Mayday PAC and CounterPAC have similar teams of advisers: They both include Greer, Lessig, GOP consultant Mark McKinnon, Republican campaign finance attorney Trevor Potter and Kahlil Byrd, chief investment officer of Fund for the Republic, a nonprofit working to reduce the influence of special interests. The Fund gets backing from members of Democracy Alliance, a group of top liberal donors.

Officials said the super PACs share similar missions but are separate projects.

"It’s a loose coalition of groups that have overlapping donors and overlapping leadership, but it's not a formal connection," Greer said.