Dissatisfaction at the two-party duopoly in Washington, fed by a bipartisan-media-controlled two-party state that presently strangles our country and works to amplify this stalemate for the interest of readership and corporate profit.
I adore Hillary; it's a shame that Hillary has unwittingly become part of that status quo, because her stellar resume would otherwise seal the deal with the American public. But Bernie Sanders is far more reflective of the issues that people (including many progressives) have yearned for, with little to show for from the Democratic establishment.
We'll see if Hillary can survive this anti-duopoly up-swelling better than the incumbent Republicans on their side. So far, she's maneuvering much more gracefully than those candidates.
Here's a succinct 3-step proposal for any candidate to propose, in order to address the dynamic described above:
1. End the electoral college.
2. Automate allocation of districts to end gerrymandering.
3. End first-past-the-past voting; replace with ranked-ballot (instant runoff) elections.
This would enable the multifaceted conversation that's going on around the country, thanks to us having more than two choices, without fracturing the large tent of the mainstream parties. Think if we had a system that rewarded candidates and parties for offering choice, rather than punish them with a system that stokes division rather than drive collaboration.
Whatever your party affiliation, the 3 steps outlined would likely benefit your candidate, but without driving the wedge that the "other guys" are likely trying to exploit. When our politics are so sorely constrained by gamesmanship, it's time to shake up the game, and change the rules a little bit.