BRUNSWICK

Former Gov. Angus King, the presumed front-runner in the race to replace Olympia Snowe in the U.S. Senate, said Wednesday he’ll discourage spending by outside groups on his behalf if his opponents do the same.

King, who is running as an independent, called such spending “a tidal wave of anonymous campaign expenditures that distort our political process.”

King’s two major-party opponents, Democrat Cynthia Dill and Republican Charles Summers, said in statements Wednesday that they were not prepared to make a commitment against super-PAC money. Dill said she found King’s proposal “lacks any detail or substance,” and Summers said it was “yet another effort to distract Maine voters from the real issue in this campaign: the economy.”

King said during a press conference Wednesday that he sent a letter to the other Senate candidates that morning challenging them to condemn this spending, too.

“I think the people of Maine deserve to know where the money is coming from that is attempting to influence the outcome of this election,” said King. “It’s taken accountability away from the candidates. People can say, ‘I didn’t have anything to do with that scurrilous attack because it was independent.’”

Dill said she is interested in exploring King’s proposal and fleshing it out with concrete details.

“This issue is of great concern to me and the people of Maine,” said Dill in a written statement. “The letter, however, lacks any detail or substance.

Given the number of candidates in the race and the vast disparity of personal wealth among them, the devil will be in the details. We look forward to seeing a proposed agreement, the terms of which would be carefully considered.”

In a statement in reaction to King’s press conference, Summers declined to say whether he would consider the proposal and instead focused on issues such as the economy and cutting government spending.

“While working Mainers are struggling to find good jobs and take care of their families, Angus King would rather discuss the intricacies of campaign finance,” said Summers. “This is exactly what is wrong with Washington. My campaign will not be centered on the tit-for-tat gimmickry of Washington politics. The people of Maine have had enough of that.”

Asked whether he would distance himself from super- PAC money regardless of whether the other candidates in the race do, King said he was not prepared to make that commitment Wednesday.

“My inclination is to do so but on the other hand I don’t like to go into a fight with one hand tied behind my back,” said King.

King already has benefited from nearly $24,000 in super- PAC money from a group called icPurple Inc., which produced an online advertisement supporting him, according to campaign finance reports. The only other outside, independent expenditures in the Senate race so far came from the Freedom- Works for America political action committee, which spent about $30,000 supporting State Treasurer Bruce Poliquin’s Republican Senate candidacy. Poliquin finished second in the GOP primary.

King’s latest campaign finance report on file with the Federal Election Commission also shows he took in $8,000 in contributions from political action committees. Of that amount, $5,000 came from Google’s political action committee

Google NetPAC.

King also received $1,000 from timber giant Plum Creek’s Good Government Fund; $1,165 from the Council for a Livable World Candidate Fund, a group that supports mostly Democrats and favors “reducing the danger of nuclear weapons;” and $500 from Politics 180, a Massachusetts based political action committee that says it wants to “tone down the partisanship in politics.”

Neither Summers nor Dill has benefited yet from any independent expenditures, but both campaigns have received some measure of support from outside committees.

Summers, along with most of his Republican primary rivals, accepted a $5,000 check from the Alamo PAC in early March. The Alamo PAC is affiliated with Sen. Jon Cornyn of Texas, who is chairman of the National Republican Senatorial Committee.

Dill accepted a $500 contribution from the Massachusetts based Women’s Action for New Directions fund in early April.

In Massachusetts, Sen. Scott Brown, a Republican, and his Democratic challenger, Elizabeth Warren, reached an agreement similar to what King proposed Wednesday.

Under federal election law, candidates are not allowed to coordinate with third-party groups, often called super- PACs, so Brown and Warren had to find an innovative way to discourage spending by these independent political action committees.

Called the “People’s Pledge,” the pact requires a candidate who benefits from a thirdparty ad to pay a penalty. The money goes to a charity chosen by the other candidate.

In a letter they wrote to third-party groups earlier this year, Warren and Brown said: “Your spending will damage the candidate you intend to help.”

The pledge is credited with helping improve the tone of the Massachusetts Senate race.

While voters said they liked the pledge for curbing nasty attacks, the outside groups said they saw the pledge as an infringement on their speech rights.

Republican strategist Todd Domke told NPR: “At some point (independent groups) will probably say, ‘Forget the People’s Pledge … We’re people, too. It’s time to go to war.’”

In November 2010, the Republican State Leadership Committee spent $400,000 on fliers and ads in five Maine state Senate races. Many of the Republican candidates said they disapproved of the spending on their behalf.

In February, the Maine Ethics Commission fined the committee $26,000 for failing to file timely and accurate reports about the expenditures. It is the largest fine in the agency’s history.

Ultimately, the commission determined that the late filings delayed $160,000 in matching payments through Maine’s public campaign financing program to the targeted Democrats, all of whom lost their campaigns to GOP opponents. Those GOP victories also helped Republicans gain control of the Senate.

BANGOR DAILY NEWS writer Matthew Stone contributed to this report. For more, see the Bangor Daily News at bangordailynews.com.