Why are they keeping Lessig out? According to Lessig, it's for the same reason he wants in: "My view is that if we can get this message [of reform] into the debate it would change the dynamics of this Democratic primary entirely. This issue framed in this way totally blows up the Democratic primary."
Hillary and Bernie, he says, are promising the moon to voters, but can't deliver. Lessig told me, "If I can get on that stage and say the rocket can't get off the ground, and we have to change this dynamic first," the narrative shifts in a way that the leading candidates can't address.