Fireworks exploded in the sky and caravans of supporters celebrated in the streets, waving red flags and honking horns. Thousands of people gathered outside Miraflores Palace, where the former paratroop commander appeared on a balcony to sing the national anthem and address the crowd.
"Those who voted 'yes' today voted for socialism, for revolution," Chavez said. He called the victory - which allows all public officials to run for re-election indefinitely - a mandate to speed his transformation of Venezuela into a socialist state.
"Today we opened wide the gates of the future," he said. "In 2012 there will be presidential elections, and unless God decides otherwise, unless the people decide otherwise, this soldier is already a candidate."
With 94 percent of the vote counted, 54 percent had voted for the constitutional amendment, National Electoral Council chief Tibisay Lucena said. Forty-six percent had voted against it, a trend she called irreversible. She said turnout was 67 percent.
At their campaign headquarters, Chavez opponents hugged one another, and some cried. Several opposition leaders said they wouldn't contest the vote.
"We're democrats. We accept the results," said opposition leader Omar Barboza.
But they said the results were skewed by Chavez's broad use of state resources to get out the vote, through a battery of state-run news media, pressure on 2 million public employees and frequent presidential speeches which all television stations are required to air.
Opponents say Chavez already has far too much power, with the courts, the legislature and the election council all under his influence. Removing the 12-year presidential term limit, they say, makes him unstoppable.
"Effectively this will become a dictatorship," Barboza told The Associated Press. "It's control of all the powers, lack of separation of powers, unscrupulous use of state resources, persecution of adversaries."
Voters on both sides said the referendum was crucial to the future of Venezuela, a deeply polarized country where Chavez has spent a tumultuous decade in power channeling tremendous oil wealth into combating gaping social inequality.
Chavez supporters say their president has given poor Venezuelans cheap food, free education and quality health care, and empowered them with a discourse of class struggle after decades of U.S.-backed governments that favored the rich.
"This victory saved the revolution," said Gonzalo Mosqueda, a 60-year-old shopkeeper, sipping rum from a plastic cup outside the palace. "Without it everything would be at risk - all the social programs, and everything he has done for the poor."
Chavez took office in 1999 and won support for a new constitution the same year that allowed the president to serve two six-year terms, barring him from the 2012 elections. Sunday's vote was his second attempt to change that; voters rejected a broader referendum in December 2007.
Venezuela's leftist allies in Latin America have followed the model. Ecuador pushed through a new constitution in September and Bolivia did so in January. Both loosened rules on presidential re-election. Nicaragua's ruling Sandinistas also plan to propose an amendment that would let Daniel Ortega run for another consecutive term.