Elizabeth Warren is, I think, a great demonstration of the kind of movement-oriented model-wielding power from within the Senate. Over and over, she's rallied tons of people to battles that they don't normally get involved in.

When [Bernie] Sanders was challenged about how he would pass his visionary ideas after he became president, he talked about if lawmakers look out the window and they see a million people marching, it changes their calculus. Well, here's an opportunity to continue working to organize these million people even if he is not the one in office.

There is a question as to whether these rallies [2016] are going to stop in the fall. I think they should continue. They are a tremendous display of energy but also a source of energy, because people come out of them ready to fight.

An organization is great if you have a clear vision to be able to make it powerful. If you don't, an organization can kind of sap energy that could go elsewhere.

What he [Bernie Sanders] does next will really determine whether he is blazing a trail that others can follow into office, or whether he is an exception to the rule.