“THIS REVOLUTION doesn’t just depend on one person,” Hugo Chavez told Venezuelans in a television address Saturday night. Sadly for Mr. Chavez, that claim may soon be tested. The 58-year-old caudillo, who has been suffering since early last year from an undisclosed form of cancer, has returned to Cuba for more surgery — and is sick enough to have named a successor in the event he is unable to remain in office.

Mr. Chavez’s incapacitation could tip Venezuela, one of the largest U.S. oil suppliers, toward a prolonged period of turmoil or even violence. If so, it will be due not so much to his illness but to the breathtaking irresponsibility with which he has responded to it. Mr. Chavez did not tell Venezuelans he was ill until after he had already undergone at least one cancer surgery in Cuba; to this day he has not said what type of cancer he has or what his prognosis is. Twice he has declared himself fully cured, most recently when he launched this year a campaign for a new six-year term as president. Almost immediately after his victory in the Oct. 7 vote, Mr. Chavez disappeared from view — a strong indication that he deceived the millions of voters who supported him.

Mr. Chavez is now saying that his longtime foreign minister, Nicolas Maduro, should succeed him. But he cannot appoint him to office: Venezuela’s constitution says that if the president dies or is forced to leave office, a new election for president must be held within 30 days. There is no guarantee that Mr. Chavez’s populist movement can hold together after his death or that Mr. Maduro could defeat a challenger from the Venezuelan opposition. Polls have consistently shown that the opposition candidate in the October election, Henrique Capriles Radonski, could defeat any government nominee except Mr. Chavez.

Mr. Chavez has meanwhile ensured that whoever succeeds him will inherit a daunting mess. To win the election, the government spent wildly, running up a budget deficit of 20 percent of gross domestic product. The next president consequently will be forced to devalue the currency, giving a boost to inflation that is already in double digits and worsening already-severe shortages of consumer goods. That’s not to mention the tidal wave of violence that has overtaken the country: Venezuela’s murder rate is now one of the highest in the world.

In 14 years in power, Mr. Chavez has thoroughly wrecked what was once Latin America’s richest country and one of its most enduring democracies. Now, thanks to his dishonesty about his health, he could create a vacuum in which Venezuelans have 30 days to decide on a leader to inherit the catastrophe he created.