Henrique Capriles, a young governor who ran a spirited but unsuccessful effort to unseat President Hugo Chavez in an October election, said Sunday that he will run against the late president’s handpicked successor in a snap vote that will determine the future of the late leader’s self-styled socialist revolution.

Capriles, 40, said he will accept the nomination of a coalition of opposition groups to face off on April 14 against Nicolas Maduro, who served Chavez as vice president until Chavez died Tuesday after a long ordeal with cancer. On Friday, Maduro, 50, was inaugurated president and vowed to continue Chavez’s radical agenda to remake this OPEC nation as a show of “the most absolute loyalty to the commander, Hugo Chavez.”

Polls show Maduro would win an election against Capriles. The outpouring of emotion for the late president, who is glorified in 24-hour coverage on state television as a mythical visionary who transformed Venezuela for the betterment of its poor masses, is expected to be transferred to Maduro.

But Capriles said he will not back down, even though he had been casually told by someone earlier in the day that he was being “led to a slaughterhouse.”

“I want to tell our people — from here inside, clinging to God, in whom I believe — that I am going to fight,” Capriles said, in a pointed address in which he accused the government of using Chavez’s death to campaign.

“Nicolas,” Capriles said, speaking directly to Maduro, “I am not going to leave you an open road, friend. You will have to defeat me with votes. I am going to fight with these hands. I’ll fight for each vote.”

Capriles said the government had known that Chavez was dying and had been laying the groundwork for decisions by the Supreme Court and the electoral board that permitted Maduro to run after the populist leader’s death.

“They’ve been lying to the Venezuelans,” Capriles said. “All this was coldly calculated, when they would hold elections, the chronogram for the whole electoral process.”

He added: “Who knows when President Chavez died? You had everything fixed.”

Maduro, in a live speech, called Capriles’s accusations “a declaration of war.”

“What’s been said is grave, very grave,” he said. “It’s the worst that we could have expected.”

Chavez’s cancer was a state secret, and the public was never told what kind of tumor he had.

Maduro, in his inaugural address, spoke about Chavez’s ordeal and revealed that the president believed as early as June 2011 that the tumor was severe.

“He told us, ‘This is worse than what you think or what the doctors say,’ ” Maduro said, recounting discussions in Cuba, where Chavez was treated.

Chavez, however, would later announce publicly that he had been cured on two occasions.

Maduro also said in his speech that in December, Chavez’s “intuition” was that he was not going to emerge from the operation that awaited him in Havana. Indeed, Chavez never recovered from the Dec. 11 surgery. Still, Maduro and other officials often spoke hopefully about the president’s health in the weeks that followed, even saying he was running the day-to-day affairs of state.

Capriles also said the government violated the constitution because the head of congress should have been designated interim leader upon Chavez’s death. The elevation of Maduro to acting president, Capriles said, allowed the government to get around an article in the constitution that bars sitting vice presidents from running for the presidency.

It is easy to see why Capriles would not want to face Maduro.

For many Venezuelans, El Comandante’s last directive is ingrained: On Dec. 8, Chavez told his countrymen in his final public comments that they should throw their support behind Maduro if Chavez became unable to govern.

“I ask you that from my heart,” he said in what turned out to be his farewell to the nation.

“He will be our president because our commander gave the order to put him there in power,” said Gregorio Villamizar, 38, who said he worshiped Chavez and would follow any of his orders. “He was a Chavez ally, the successor to Chavez, and he was the only one Chavez prepared to take power.”

Luis Vicente Leon, director of a Caracas-based polling company whose surveys show Maduro with more support than Capriles, has said that because the election is coming so soon after Chavez’s death, many will see it as a contest between Capriles and Chavez.