BRUNSWICK — Former Gov. Angus King announced this morning that he has sent a letter to all the candidates in Maine’s U.S. Senate race asking them to adopt an agreement to eliminate the influence of unregulated third-party campaign spending.

The agreement would be similar to one now in use in the U.S. Senate race in Massachusetts, in which Republican incumbent Scott Brown and Democratic challenger Elizabeth Warren have agreed to donate the same amount of money to charity whenever third-party money is spent on their behalf.

King said he is frustrated that he has to record and disclose the source of even a $10 campaign contribution, while independent super PAC money does not face similar requirements.

He said the third-party money – the result of the U.S. Supreme Court’s Citizens United ruling two years ago – has created a system in which there is no accountability in how campaign money is spent.

“This money is destroying our politics,” he said. “It’s a question of fundamental honesty. The people of Maine should know who’s influencing these campaigns.”

King said he sent the letters to all five of the other candidates running for the U.S. Senate seat being vacated by Olympia Snowe, including Democrat Cynthia Dill, Republican Charlie Summers and the three other candidates running as independents: Steve Woods of Yarmouth, Danny Dalton of Brunswick, and Andrew Ian Dodge of Harpswell.

Democratic nominee Cynthia Dill said in a statement this afternoon that she appreciates the overture by King to have a dialogue about the corrupting influence of money on politics, which she described as an issue of great concern to her.

However, she said, King’s proposal lacks 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,” she said. “We look forward to seeing a proposed agreement, the terms of which would be carefully considered.”

Republican nominee Charlie Summers in a statement today rejected King’s proposal. Summers said his campaign will not get involved in the “tit-for-tat gimmickry of Washington politics” and added that King is trying to distract voters by talking about the intricacies of campaign finance rather than the economy.

“This is exactly what is wrong with Washington,” he said.