Five Democrats seeking their party's nomination to fill U.S. Sen. Edward Markey's former House seat have signed a deal aimed at keeping outside advertising out of the race.
The agreement is modeled after the "People's Pledge" that originated in the 2012 Senate race between Democrat Elizabeth Warren and Republican Scott Brown.
The Democratic Party announced Tuesday that the pact was signed by 5th Congressional District candidates William Brownsberger, Katherine Clark, Peter Koutoujian, Carl Sciortino and Karen Spilka.
Their pledge (PDF) works slightly differently than previous iterations. If an outside group runs an ad in support of or against one candidate, the candidate who was endorsed by that group will donate an amount equal to 50 percent of the cost of the ad to The One Fund, the charity that helps Boston Marathon bombing victims.
The pact covers television, radio, satellite and online advertising.
The five candidates also agreed to release a message stating that a pledge violation has occurred if an outside group that has not endorsed a candidate runs an ad against or in favor of one candidate.
Two other Democrats and three Republicans will be on the Oct. 15 primary ballot.
With reporting by The Associated Press and the WBUR Newsroom
This program aired on August 20, 2013. The audio for this program is not available.