Here's an idea - an attack candidate

Democrats need somebody that does not ever expect to win. Somebody that can run, get on TV, and in debates. And that person just nails Trump in a way the others can't. Think about that. A candidate that comes on TV and just flat out says Trump is a moron. That he is a lying racist con man. And sticks some label on Trump - like "Comrade Trump" - In every interview, they refer to Trump as "Comrade Trump" and do it in debates too. Then the rest of the field can be respectful and nice and let Trump have a dose of his own medicine. Just a thought.