They are unified in what they represent: a shock to the system and a chance at actual change of the sort we keep being promised by mainstream candidates. Whether they’d actually be able to pull it off is a whole other question, but it’s hard to paint either one as an establishment candidate. People are so sick of politics as usual that they’re willing to try burning the system down to see if that helps. And that’s why I keep having the odd experience of meeting people who are having a tough time picking between voting for Trump or voting for Sanders despite the vast difference in their political positions (I live in an open primary state, so we’ll get to make this decision at least once). A lot of people are more worried about politics itself than policy right now—or at least willing to temporarily ditch their policy concerns if it means upsetting the political establishment.