Social scientists thought that patrimonialism had been relegated to the dustbin of history. And for good reason: Such regimes couldn’t compete militarily or economically with states led by the expert civil services that helped make modern societies rich, powerful and relatively secure.

But a slew of self-aggrandizing leaders has taken advantage of rising inequality, cultural conflicts and changing demography to grab power. The result has been a steep decline in the government’s ability to provide essential services such as health care, education and safety.