I have long thought it was unfair for the general public to select a political party's candidates, people who have never given time nor a dime to that party. Neither Sanders nor Trump are party members, but they both presumed a right to run in party primaries.
Arthur C. Brooks gave a great parallel in his conversation with Gail Collins. See http://www.nytimes.com/2016/07/29/opinion/the-democrats-nailed-it-does-it-matter.html.
"It amazes me how we have come to see democracy in all matters, public and private, as our natural right. Can you imagine if The New York Times had a policy of letting the readers unilaterally decide who writes for the Op-Ed page? It would make the paper into an ideological fever swamp."