More than a farewell, this “sea of red” in the streets was a dramatic display of how completely the leader of the so-called Bolívarian revolution for “21st-century Socialism” has kept Venezuela and much of Latin America in thrall for nearly a generation. As mourners wept and punched the air in grief, the heads of states of a dozen Latin nations flocked to the Venezuelan capital to pay tribute to the mercurial man of the people, whom Brazilian President Dilma Rousseff described as “a great leader, an inspiration, and a great friend.”

The public outpouring was a hint of the anguish still to come as this nation of 28 million comes to grips with the sudden absence of the outsize firebrand who put populism on steroids, made a sport of hectoring the superpowers, and now stands shoulder to shoulder with Latin icons like Cuba’s Fidel Castro and Argentina’s Juan Domingo Perón. “Chávez didn’t die. Chávez lives on in the people,” chanted the mourners in the funeral cortege, bringing downtown Caracas to a halt.

Beyond the commotion, uncertainty and apprehension loom. According to the Venezuelan Constitution—a document often quoted, but rarely followed—a new election must be called within 30 days. Already, pretenders to Chávez’s seat are jockeying for advantage. Pollsters tout the advantage of acting president Nicolás Maduro, who was Chávez’s handpicked heir and looks best placed to ride the wave of sympathy into the Palacio de Miraflores. The most likely challenger is Henrique Capriles Radonski, a 40-year-old governor who galvanized the fractured political opposition to run against Chávez in the October elections, falling a respectable 11 percentage points short of an upset....