Massachusetts State Treasurer Steven Grossman, who is one of five Democrats currently running for Governor, issued a challenge to his rivals this week. He called on them to sign the so-called “People’s Pledge.” This ban on third-party campaign advertising was popularized in the 2012 race for U.S. Senate between Scott Brown and Elizabeth Warren. WAMC”s Pioneer Valley Bureau Chief Paul Tuthill spoke with Grossman about this and other issues.