Andrew posts an extended meditation from a reader on Marc Bloch's theory, outlined in Strange Defeat that, as the reader puts it, "the extreme polarization of the 1930s fatally weakened the Third Republic, sowing disunity when the Hitlerite threat demanded precisely its opposite." It's a fascinating book, and well-worth reading (as is Ernest May's counterpoint, Strange Defeat) but it's worth saying that there are some real failures of analogy here. Indeed, the reader himself concedes:
Now, I don't mean by this that Bin Laden or Ahmedinejad are comparable with Hitler, as all the Michael Ledeens of the world would have it; the NRO crowd is seemingly incapable of understanding the inherent subtlety of historical comparison, the necessary lack of a 1:1 correspondence between any two epochs -- this is why it's always 1938 for them. However, we would be remiss if we ignored the cautionary example of another great democracy undone by political polarization.
But on top of that, though there clearly is a sense in which current American politics is very polarized, there's another sense in which our levels of polarization are almost trivial compared to 1930s France. We don't have a substantial revolutionary Communist movement here in the United States, nor a monarchist movement, nor do we have an officer's corps that's generally skeptical of civilian command and republican governance. Indeed, even compared to the United States of forty years ago when you had a lot of votes going to George Wallace on a white supremacist platform and substantial intellectual support for the idea of convergence between the Soviet and American economic models, our politics is conducted across a pretty narrow ideological spectrum.
What's new in America isn't polarization in that sense, but the rise of partisan polarization organized around two fairly coherent political parties. The good news about this is that it's mostly an inevitable consequence of the decline of Jim Crow. The bad news is that the country has a set of political institutions that weren't designed with competition between two ideologically coherent parties in mind. That's creating a lot of problems, a lot of frustrations, and a lot of intra-party tensions. But it's not nearly the same thing as a society being ripped apart over the sort of profound ideological differences you saw in interwar Europe.