Populism

Here is a really handy definition of what populism is.  It isn't "popular."

What is important is that populism's focus on the "people" over "elites" makes representative government dysfunctional, unless you channel the "popular will" through a charismatic leader who can claim to represent the people.  This is why most demagogues are populists.

It's also why a guy like Trump is going to fail.  He can't "run the government" because he's fundamentally at odds with the idea of representative government.  And then his policies are increasingly at odds with what "the people" want.