In Mass. Senate Race, A Debate Over 'Attack Ads'

Republican U.S. Sen. Scott Brown and Democrat Elizabeth Warren say they want to block third-party groups from launching political attacks ads in the race for the Senate seat now held by Brown.

What's less clear is just what power Brown or Warren have over the independent groups behind the ads.

By their nature, the political action committees and outside groups that pay for the ads must work independently of the candidates and their campaigns. Federal election law explicitly bans candidates from coordinating with the committees on advertising.

Brown was the first to call on third-party groups to eliminate the ads, which he called "false and misleading."

Warren initially defended some of the ads. But last week she suggested that she and Brown should forge an "enforceable agreement" to block them.