ATLACOMULCO, Mexico — It’s in the names of streets and on some of the most prominent buildings. It’s embedded in the colorful murals that adorn the walls of city hall. It’s infused into the local history and lore. And most important, it’s reflected in the way the population has voted for decades.

For generations, the Institutional Revolutionary Party has been central to the identity of Atlacomulco.

The mostly rural municipality, about 50 miles northwest of Mexico City, is often called the cradle of the political party, known as the PRI, which has governed Mexico for most of the last century.

During the decades the PRI dominated Mexico, the centrist party perfected the art of political patronage and took good care of its own. This seems evident in Atlacomulco de Fabela, the municipal seat, a quiet town of narrow streets.