He describes what populism is and stands for, in its many forms: the only true representative of "the people", the true representatives of moral values, against the immoral elites, against the establishment, waging an apocalyptic war against the secret and oppressing forces. Their enemies are the press, intellectuals and civil society.
He explains how populism is created by the strong democratic deficit of open debate and the rule of technocrats whose language not only doesn not appeal to the general population, but which is also not directed to them. Specifically in the US, the economic interests of a significant part of the population is underrepresented in Washington.
When populists gain power, they will, interestingly enough, not bring politics "closer to the people" or even reasserting popular sovereignty.
He mentions a number of solutions, which is of course a much more open and public debate on the topics that are on people's minds, including a good democratic representation (but not through referenda!).