From Christopher Browning’s NYRB review of Volker Ullrich’s Hitler: Ascent 1889–1939:

Hitler and National Socialism should not be seen as the normal historical template for authoritarian rule, risky foreign policy, and persecution of minorities, for they constitute an extreme case of totalitarian dictatorship, limitless aggression, and genocide. They should not be lightly invoked or trivialized through facile comparison. Nonetheless, even if there are many significant differences between Hitler and Trump and their respective historical circumstances, what conclusions can the reader of Volker Ullrich’s new biography reach that offer insight into our current situation?

First, there is a high price to pay for consistently underestimating a charismatic political outsider just because one finds by one’s own standards and assumptions (in my case those of a liberal academic) his character flawed, his ideas repulsive, and his appeal incomprehensible. And that is important not only for the period of his improbable rise to power but even more so once he has attained it. Second, putting economically desperate people back to work by any means will purchase a leader considerable forgiveness for whatever other shortcomings emerge and at least passive support for any other goals he pursues. As James Carville advised the 1992 Clinton campaign, “It’s the economy, stupid.” Third, the assumption that conservative, traditionalist allies—however indispensable initially—will hold such upstart leaders in check is dangerously wishful thinking. If conservatives cannot gain power on their own without the partnership and popular support of such upstarts, their subsequent capacity to control these upstarts is dubious at best.

Fourth, the best line of defense of a democracy must be at the first point of attack. Weimar parliamentary government had been supplanted by presidentially appointed chancellors ruling through the emergency decree powers of an antidemocratic president since 1930. In 1933 Hitler simply used this post-democratic stopgap system to install a totalitarian dictatorship with incredible speed and without serious opposition. If we can still effectively protect American democracy from dictatorship, then certainly one lesson from the study of the demise of Weimar and the ascent of Hitler is how important it is to do it early.