Massachusetts Sen. Scott Brown and his chief 2012 rival Elizabeth Warren made history when they signed a "People's Pledge" to limit the influence of third party interest groups and Super PACs in their hotly watched Senate race.

But with the ink still wet, the newly minted Massachusetts pact is already unraveling.  The pledge by Brown, a Republican, and Warren, a Democrat, to expel third party interest groups from their race was written by one of the third party groups the pledge sought to block, the Huffington Post reported Monday.

The pledge that Brown sent out to reporters as a Microsoft Word document was created by Sean Caincross, the top lawyer for the National Republican Senatorial Committee, according to the document's electronic signature.

The NRSC is a national group that works to elect Republicans to the Senate. The group's spokesman Brian Walsh told the Huffington Post that NRSC's involvement "shouldn't surprise anyone."

"As with our Democratic counterparts, the NRSC frequently provides advice and counsel to all of our campaigns," Walsh said.

As the Massachusetts anti-PAC pact falters, a similar attempt to  implement an anti-outside-influence agreement in the Montana senate race is crumbled Monday.

Incumbent Sen. Jon Tester challenged his Republican rival Rep. Denny Rehberg to sign an agreement last week to reject donations or money spent on their behalf from third party groups outside of Montana.

"It's a shame that third-party organizations are allowed to pollute our records and drag our character through the mud with no transparency and no accountability," Tester wrote Wednesday in a letter to Rehberg. "Let's let only you and me - and our campaigns- do the work of illuminating the issues and the differences that separate us."

Rehberg responded Friday by taking Tester's pledge a step farther. Instead of only limiting money from out-of-state groups, Rehberg also wanted to block donations from  lobbyists and political action committees and called for both campaigns to return any money already received by such people or organizations.

Tester rejected the counter-proposal Monday, saying Rehberg can't be trusted to adhere to such an agreement. The Tester's campaign manager Preston Elliott said in a statement that Rehberg's response was "just more dishonest politics."

Erik Iverson, Rehberg's campaign manager denounced Tester's decision Monday evening.

"By rejecting that proposal Senator Tester is admitting there simply isn't enough support in Montana for the failed policies he and President Obama have given us," Iverson said in a statement.