Many people are reacting to the rise of Trumpism and nativist movements in Europe by reading history — specifically, the history of the 1930s. And they are right to do so. It takes willful blindness not to see the parallels between the rise of fascism and our current political nightmare.

But the ’30s isn’t the only era with lessons to teach us. Lately I’ve been reading a lot about the ancient world. Initially, I have to admit, I was doing it for entertainment and as a refuge from news that gets worse with each passing day. But I couldn’t help noticing the contemporary resonances of some Roman history — specifically, the tale of how the Roman Republic fell.

Here’s what I learned: Republican institutions don’t protect against tyranny when powerful people start defying political norms. And tyranny, when it comes, can flourish even while maintaining a republican facade.

On the first point: Roman politics involved fierce competition among ambitious men. But for centuries that competition was constrained by some seemingly unbreakable rules. Here’s what Adrian Goldsworthy’s “In the Name of Rome” says: “However important it was for an individual to win fame and add to his and his family’s reputation, this should always be subordinated to the good of the Republic … no disappointed Roman politician sought the aid of a foreign power.”