These are two chapters from the book How Democracies Die. They chart the erosion of norms among high level politicians in the US. The authors find this worrisome because it reminds them of the countries they study. Levitsky studies Latin American politics while Ziblatt’s work is on the reaction of conservative parties in Europe to democratic government in the early 20th century.
They have an editorial in the New York Times about Trump.
Having read it, I am struck by their omission of a sixth pathway to defeating a candidate like Trump: compromise. Trump has even odds of winning because a significant portion of the population is worried about immigration. That, not coincidentally, seems to be what motivates a lot of support for some of the other right wing parties they mention. But the opponents of these parties are not helpless. They can adopt a more popular position on immigration. Indeed, that is what the Democratic party did, although very late in the game. Offering to do things that the people want is the most democratic pathway of all.
Anyway, while you are enjoying the Times, you can take a gander at an article about Adam Przeworski, another political scientist who has spent a lot of time thinking about how democracy might fail.