Hugo Chavez could have a shot at becoming president for life if voters approve a sweeping overhaul of the constitution Sunday that would give him unchecked power to reshape Venezuela's government, economy and society.

Some polls show Chavez faces considerable resistance in the referendum. His primary impediment seems to be voters like Vanessa Meneses, a 27-year-old single mother who has backed Chavez in past elections but now fears he could become another Fidel Castro.

"Supposedly he wants to make Venezuela like Cuba and stay in power forever. It's scary," Meneses said. "He wants to be the only one like in Cuba, and I don't like it."

Venezuelans across the political spectrum see the vote as a turning point for their country — and perhaps a point of no return. The changes to 69 of the constitution's 350 articles would enshrine a socialist economic system, create new classes of property to be managed collectively and let Chavez stand for re-election in 2012 and beyond.

Chavez has sold these changes by capitalizing on his personal popularity — he is seen by many Venezuelans as their savior, spreading more oil wealth among the poor than any leader in memory.

A "yes" vote keeps him on as captain of a ship that otherwise "could sink," he warns. His image is everywhere — even the Caracas subway plays a rap-style campaign jingle for Chavez.

The former lieutenant colonel, now 53, insists he will stay in power for as long as his people want him to — perhaps into the 2030s, or for life.

"If you wish — and if you approve the referendum — I will stay as long as God wills! Until the last bone of my skeleton dries up! Until the last bit of my body dries up!" he shouted to the applause of thousands.

Opponents — including Roman Catholic leaders, press freedom groups, human rights groups and prominent business leaders — fear the reforms will remove some of the last checks on Chavez's power.

Students are proving to be a particular challenge, leading street protests and occasionally clashing with police and Chavista groups. One man was shot dead Monday while trying to get through a road blocked by protesters. A large opposition march is planned for Thursday, along with pro-Chavez rallies.

The amendments would remove term limits, extend presidential terms from six to seven years, grant Chavez direct control over the Central Bank and monetary policy, allow his government to detain citizens without charge during a state of emergency, and let the state occupy private properties it wants to expropriate.

He also would be empowered to redraw the country's political map and handpick provincial and municipal leaders — a change opponents fear will push aside any elected officials who aren't his allies.

"The only certain thing that emerges is a total concentration of political power in Chavez's fist," opposition politician Teodoro Petkoff wrote in his newspaper Tal Cual. He calls the changes a "Plan for Venezuela's Destruction." Other opponents have taken out newspaper ads urging voters to "defend democracy."

Yet many Chavistas see real benefits in these and other amendments — such as shortening the workday from eight hours to six, creating a social security fund for millions of informal laborers and promoting communal councils where residents decide how to spend government funds in their neighborhoods.

"It's power for the people. It's not power for me," says Chavez — a theme also promoted by his leftist allies trying to rewrite the constitutions of Bolivia and Ecuador. Smiling in a TV campaign commercial, Chavez tells viewers: "I want you to be the center of power."

Many voters confess they don't understand all the changes, but will vote based on how they feel about Chavez.

"I think people want him to stay on until he has consolidated our process, and may God give our Comandante a long life," said Gladis Gonzalez, 50 and studying law at a free state university.

Others say they'll vote "yes" because the new constitution guarantees that oil-funded "missions" will keep offering free health care and education.

But shopkeeper Maria Teresa Gonzalez said she has lost faith in Chavez after seeing rampant murders in her part of Caracas, and shortages of milk and other goods. If he were successful, "things would have changed and gotten better. And they're getting worse."

If approved, the revisions would create an unprecedented "centralization of power" in the president's hands, said Jose Vicente Haro, a constitutional law professor at Caracas' Andres Bello Catholic University. "In nearly 50 years of democracy, it would be the constitution that has given him the most power."

Chavez, first elected in 1998, already obtained total control of the National Assembly when opponents boycotted the 2005 elections, and lawmakers gave him special powers to enact some laws by decree through next June.

This constitution would go much farther, Haro said. One of the most profound changes would come in a little-noticed "transitory" clause appended at the end, which Haro believes would let Chavez enact laws by decree for an unlimited period — possibly for years — to hasten a "transition to the Socialist Economic Model."

Chavez himself has said more than 100 new laws would be required if the referendum passes — and that he will waste no time in making that happen.

The opposition is urging voters to turn out in large numbers on Sunday, hoping Chavez may be vulnerable after some prominent defections from Chavez's movement, including former Defense Minister Gen. Raul Baduel and lawmakers of the small left-leaning party Podemos. Even Chavez's ex-wife Marisabel Rodriguez has urged Venezuelans to vote "no," saying the changes would be like a "leap into the dark."

The government cites polls suggesting Chavez has an advantage, while the Caracas polling firm Datanalisis — in a nationwide survey this month — found 49 percent of likely voters opposed Chavez's reforms and 39 percent were in favor.

While the pollster has predicted some of Chavez's past victories, its results haven't always been on-target. A poll released by the firm in June 2004 found that 57 percent of Venezuelans would vote to recall Chavez, but the president handily won the vote two months later.

Chavez predicts a "knockout" but acknowledges it might be a smaller margin than his re-election last December, when he won 63 percent of the vote.