Chavez, in a nationwide address over the weekend, said he was throwing his “irrevocable, absolute” support behind Vice President Nicolas Maduro to lead his 21st century socialist revolution should he be unable to carry out his duties. Chavez made the comments before flying to Cuba before dawn today for surgery, his fourth in 18 months, to treat an undisclosed form of cancer that reappeared after winning re-election in October.

Maduro, a former bus driver and union leader, has been one of Chavez’s closest civilian allies since the then-tank commander first attracted national attention by leading a failed 1992 coup. While the president’s endorsement carries weight with Chavez’s base among the poor, a succession battle involving the more business-friendly, military wing of his movement and against a revitalized opposition is only beginning as the strongman’s grip on power weakens.