There's been a lot of debate lately among Massachusetts Democrats about party purity – what Democrats should believe, what principles or policies might be anathema (charter schools, anyone?), and what should happen to elected officials who deviate from the desired orthodoxy.

The Scrum, naturally, is intensely interested in this back-and-forth. So we asked State Senator Jamie Eldridge, an impassioned progressive who's stirred the pot with talk of intra-party challenges, and political scientist Peter Ubertaccio, who's warned Democrats not to eat their own, to join us at the Boston Public Library and rap. If you're interested in Massachusetts politics, a/k/a #mapoli, the ensuing conversation is well worth a listen – wherever your party and ideological loyalties lie.