Last Sunday, as the red carpet arrivals began at the Oscars, a scene out of a Hollywood thriller unfolded far away in the capital of El Salvador. Dozens of police officers and soldiers in full battlefield regalia, armed with assault weapons, burst into the country’s Legislative Assembly. Stunned legislators watched as President Nayib Bukele marched in and sat in the chair of the president of the assembly. “Now,” he declared, “I think it’s very clear who has control of the situation.”

Outside the legislature, Bukele’s followers, summoned by their young, charismatic leader, were smashing pinatas meant to look like his opponents. ...