From my POV, the issue is the over promise and under delivery by both parties. Also, that we elect rock stars who are clueless about governing well.
The one thing that Sanders and Trump have in common, as Reich points out, is they appeal to a large slice of the population that feels screwed over by the system.
In Sanders' case, it is effectively distribution of wealth. Those on the left have beaten this drum long enough that the masses actually believe it is a problem.
In Trump's case, it is illegal immigrants taking the jobs from Americans.
There is clear dissemination of bad information behind it all, but this does not mean the status quo is good for us all.
Both have more in common:
1. They have successfully identified bogeymen to run against.
In Sanders' case, it is corporations and rich people. In Trump's case, it is he illegals. In both cases, it is the trade deals.
The bogeyman thing is not new to politics. Republicans ran against the USSR successfully for years (and gays and criminals...). Democrats' rhetoric has traditionally included "I will fight for..." (against some bogeyman).
2. The trade deals
Job killers. Job exporters. Etc.
This clearly has struck a chord with a lot of voters.
3. Appeal to middle class whites
The proof is in the polling data. Public policy aimed at improving the situation for minorities has had a negative effect on middle class whites. You can see the gripes about it here, by a number of posters.
Both are old white men.
4. Running against the party establishment.
Yup, the system is rigged. Another bogeyman, as well.
5. The pundits completely underestimated the viability of the two candidates
The revolt by the voter is also against the biased media. Trump at war with Fox News, Sanders supporters claim the media is in the bag for Clinton.
6. Hope and change, hopes dashed and change for the worse.
The people have seen enough of progressives running things. The hope this time is "real change" is required to effect real change.
7. The bulk of both candidates' supporters do not agree with the candidates' policy proposals.
Trump supporters routinely say they don't believe Trump means what he says about the most controversial things. Misogyny, the wall, etc. Youth voters who support Sanders are opposed to most of Sanders' proposals when polled.
