Mary Beth Sheridan

VILLA LAS ROSAS, Mexico — This time, Willy Ochoa brought reinforcements. This time, unlike the last time, he’d be ready for cartel attacks. He was accompanied by three truckloads of national guard troops. Two state police cars with flashing red lights. He rode in his own bulletproof SUV, and had a complement of muscular bodyguards.

MEXICO CITY — Claudia Sheinbaum’s resounding victory in Mexico’s presidential election has injected fresh energy into a leftist movement that has rapidly reshaped the United States’ most populous neighbor and is poised to assume far-reaching control over government. It took Mexico decades of painstaking effort to transition from a one-party state to a 21st-century democracy.