The "knowing what you know now" question is important.
It's unusual for a sitting vice president not to run for the top job.
The Sanders campaign's use of social media has led to big crowds and pathbreaking fundraising from small donors.
Sanders by himself is not enough. He needs Warren.
Can he tap into the frustration of Trump voters by showing how government can work?
Competition creates better results, and the Republican primary is proving that.
After Iowa and New Hampshire, Sanders has a steep hill to climb to gain crucial minority support.
The old rules of politics seemingly don't apply to Trump.
Wasserman Schultz's comments ignore the context behind Fiorina's time as CEO.
Can we harness the attention Trump brings and use it to engage more voters?