Mexican President Andres Manuel Lopez Obrador does not waste time with mundane political rhetoric. Long before he won the presidency on his third attempt, a year ago this month, the man better known in Mexico as AMLO had already gained a reputation for setting sky-high expectations.

The leftist veteran of Mexican politics hailed his administration as ushering in the country’s “fourth transformation”—the previous three being events no less groundbreaking than its Declaration of Independence in 1810, the War of Reform, which led to the separation of church and state in the mid-19th century, and the Mexican Revolution of 1910. ...