Still, he accepted defeat as Chavez swept to a 10-point victory margin, though it was his smallest yet in a presidential race. This time, the former army paratroop commander won 55 percent of the vote against 45 percent for Capriles with more than 90 percent of the vote counted.
Chavez will now have a freer hand to push for an even bigger state role in the economy, as he pledged during the campaign, and to continue populist programs. He's also likely to further limit dissent and deepen friendships with U.S. rivals.
Chavez spent heavily in the months before the vote, building public housing and bankrolling expanded social programs.
"I think he just cranked up the patronage machine and unleashed a spending orgy," said Michael Shifter, president of the Washington-based Inter-American Dialogue think tank.
But Shifter also noted the affinity and gratefulness Venezuela's poor feel for Chavez. "Despite his illness, I still think he retains a strong emotional connection with a lot of Venezuelans that I think were not prepared to vote against him."
"They still think that he's trying hard even if he's not delivering what he promised, that he still has their best interests at heart," Shifter said.
Chavez spoke little during the campaign about his fight with cancer, which since June 2011 has included surgery to remove tumors from his pelvic region as well as chemotherapy and radiation treatment. He has said his most recent tests showed no sign of illness.
Tensions were high Sunday night as announcement of the results were delayed.
Finally, fireworks exploded over downtown Caracas amid a cacophony of horn-honking by elated Chavez supporters waving flags and jumping for joy outside the presidential palace.
"I can't describe the relief and happiness I feel right now," said Edgar Gonzalez, a 38-year-old construction worker.
He ran through crowds of Chavez supporters packing the streets around the presidential palace wearing a Venezuelan flag as a cape and yelling: "Oh, no! Chavez won't go!"
"The revolution will continue, thanks to God and the people of this great country," said Gonzalez.
Capriles posed the strongest challenge yet to Chavez, who won by a 27-point margin in 2006 and by 16 points when he was first elected in 1998.
"I will continue working to build one country," said the wiry, 40-year-old grandson of Holocaust survivors who unified and energized the opposition while barnstorming across the country.
He said in his concession speech that he rejects the idea of two Venezuelas divided by ideology and class.
Capriles had vowed to address violent crime that has spun out of control, streamline a patronage-bloated bureaucracy and end rampant corruption, but his promises proved inadequate against Chavez's charisma, well-oiled political machine and legacy of putting Venezuela's poor first with generous social welfare programs.
Yet with a turnout of 81 percent, Chavez only got 551,902 more votes this time around than he did six years ago, while the opposition boosted its tally by 2.09 million. Chavez appeared to acknowledge the opposition's growing clout.
"I extend from here my recognition of all who voted against us, recognition of their democratic weight," he told thousands of cheering supporters from the balcony of the Miraflores presidential palace.
A Capriles victory would have brought a radical foreign policy shift including a halt to preferential oil deals with allies such as Cuba, along with a loosening of state economic controls and an increase in private investment.
Washington, which has often feuded with Chavez, declined to congratulate the president directly, but acknowledged the result.
"We congratulate the Venezuelan people for the high turnout and generally peaceful manner in which this election was carried out," said State Department spokesman William Ostick.
"We believe that the views of the more than 6 million people who voted for the opposition should be taken into account going forward," he added.
President Raul Castro of Cuba, which could have been badly hurt by a Chavez loss, was among Latin American leaders sending warm congratulations to the former paratrooper on his victory after nearly 14 years in office.
Chavez paid close attention to his military-like get-out-the-vote organization at the grass roots, stressing its importance at campaign rallies. The opposition said he unfairly plowed millions in state funds into the effort.
One pro-Chavez voter, private bodyguard Carlos Julio Silva, said that whatever his faults, Chavez deserved to win for spreading the nation's oil wealth to the poor with free medical care, public housing and other government programs. The country has the world's largest proven oil reserves.
"There is corruption, there's plenty of bureaucracy, but the people have never had a leader who cared about this country," Silva said after voting for Chavez in the Caracas slum of Petare.
Capriles told supporters not to feel defeated.
"We have planted many seeds across Venezuela and I know that these seeds are going to produce many trees," he told them at his campaign headquarters.
At many polling places, voters began lining up hours before polls opened at dawn, some snaking for blocks in the baking Caribbean sun. Some shaded themselves with umbrellas. Vendors grilled meat and some people drank beer.
Chavez's critics accused the president of inflaming divisions by labeling his opponents "fascists," ''Yankees" and "neo-Nazis," and it's likely hard for many of his opponents to stomach another six years of the loquacious and conflictive leader.
Some said before the vote that they'd consider leaving the country if Chavez won.
Gino Caso, an auto mechanic, said Chavez is power-hungry and out of touch with problems such as crime. He said his son had been robbed, as had neighboring shops.
"I don't know what planet he lives on," Caso said, gesturing with hands blackened with grease. "He wants to be like Fidel Castro — end up with everything, take control of the country."