Hugo Chávez w ill be returning soon to Caracas after undergoing cancer surgery in Havana. It will not be an easy homecoming. Last year, the Venezuelan President had two operations in Cuba to remove a “baseball size” cancerous tumor in the pelvic-abdominal area; he subsequently underwent chemotherapy both in Havana and Caracas. He then, simultaneously, began to visibly gain weight and to campaign for the upcoming presidential election, due to be held in October, which if he were to win would allow him to remain in office until 2018—giving him a 19-year spell as President. But Chávez’s cancer returned recently and is now presenting him with challenges that are as much political as medical.Two weeks ago, Chávez, 57, returned to Cuba for additional surgery, this time to remove a recurrent and smaller but also malignant tumor in the same area of his body. He announced he would undergo further radiation treatment and that the new tumor was not a product of metastasis, but simply a reappearance of the same cancer, in the same spot.We still do not know exactly what sort of cancer he is suffering from, but we do now know it is grave and recurrent. We can also surmise that his public disclosures— all forced upon him by news reports revealing his condition and prognosis—do not tell the full story. His very secrecy suggests his illness is a genuine threat to his life.This raises important political questions as we get closer to October’s election. Crucially, voters in Venezuela may wonder whom they are really voting for if they cast their ballots for Chávez. They may conclude that a vote for the incumbent is actually a vote for his older brother Adán, or for his running mate, or for someone they do not even know, since in Chávez’s Venezuela the head of state can remove his Vice President and name a new one at his discretion. They may decline to make such a choice, even if they would have otherwise voted for a healthy Chávez. As a Venezuelan pollster wrote recently in El Universal, a Venezuelan newspaper, there is a huge difference between the solidarity that an ill and courageous leader can awaken among his people and a commitment to actually vote for him.Polls show that Venezuelans are ambivalent. Chávez retains a huge lead—18%, according to the most recent survey. But the polls also show that if he were not on the ballot, the opposition candidate, the young and charismatic Henrique Capriles, would win by 13% against any other candidate from the Chávez camp.The issue then boils down to whether Chávez’s presumed recovery is sufficiently convincing to assure voters that a vote for Chávez is a vote for . . . Chávez, especially if he tones down the intensity of his campaigning and has to return to Cuba frequently for treatment. If he continues to look as terrible as he has, continues to reportedly disregard his physicians’ and even the Castro brothers’ counsel to take it easy and admit he is seriously ill, the electorate may not believe that he is capable of governing for another six years. Legions of loyal Chávez voters may abandon the idea of chavismo without Chávez.Does this matter? Yes, for three reasons. First, given Chávez’s dependence on Cuba for security and medical care, the Castros’ role in this drama is dramatically enhanced. They will have much influence in what Chávez eventually does as a result of his illness: resign and choose a successor, before or after the election, or stick it out to the bitter end. At the same time, their own dependence on Venezuelan oil and subsidies also means that the demise of the demagogue from Caracas would impose another horrific bout of hardship on the Cuban people, as there are no obvious substitutes for Venezuelan support. Second, Chávez has successfully played the role of Latin America’s premier “anti-imperialist,” populist and left-wing figure, willing to dispense enormous amounts of money to regimes of many different stripes across the hemisphere. His departure from the Latin American political scene would dramatically weaken pro-Chávez governments and parties in countries like Bolivia, Ecuador and Nicaragua.And perhaps most important, it’s hard to imagine that anyone could translate Venezuelan oil might into international clout beyond Latin America as successfully as Chávez has. Venezuela re- mains a steadfast friend of Iran and of the Syrian regime of President Bashar Assad, even as most countries have condemned Assad’s military attacks on his own people. If Chávez is no longer President, for reasons of health, politics or both, Cuba, his other Latin American partners and Iranian President Mahmoud Ahmadinejad, as well as Assad, all lose a valuable and perhaps irreplaceable ally. No minor matter, especially for them.Castañeda is a Jacob K. Javits visiting professor and a global distinguished professor at New York University