Trucks blared reveille to awaken voters on Sunday as President Hugo Chavez's crusade to transform Venezuela into a socialist state was put to the stiffest electoral test of his nearly 14 years in power.

Later, folk music poured from loudspeakers in places, mixed with a recording of Chavez's voice saying "those who love the homeland come with me."

Chavez's challenger, Henrique Capriles, united the opposition for what has become a contest between two camps that distrust each other so deeply there are concerns whether a close election result will be respected.

The stakes couldn't be higher.

If Chavez wins a new six-year term, he gets a free hand to push for an even bigger state role in the economy, further limit dissent and continue to befriend rivals of the United States.

If Capriles wins, a radical foreign policy shift can be expected along with an eventual loosening of state economic controls and an increase in private investment _ though a tense transition would likely follow until the January inauguration because Chavez's political machine thoroughly controls the wheels of government.

Many Venezuelans were nervous about what might happen if the disputes erupt over the election's announced outcome.

"Nobody trusts the other people, especially when it's their political rivals," said Maria Villareal, a teacher and Capriles supporter who stocked up on groceries Saturday. "We're in a divided country, and I think Chavez is the one responsible."

She and other Chavez critics say he has inflamed divisions by labeling his opponents "fascists," "Yankees" and "neo-Nazis," while Chavez backers allege Capriles will halt generous government programs that assist the poor.

During Chavez's final rally Thursday in Caracas, he shouted to the crowd: "We're going to give the bourgeoisie a beating!"

David Hernandez, a Chavez supporter, agreed the mood was tense but he blamed the opposition.

"Chavez is going to win and Capriles will have to accept his defeat," Hernandez said, standing next to his parked motorcycle on a downtown street. "If Capriles doesn't accept his defeat, there could be problems."

Violence flared sporadically during the campaign, including shootings and rock-throwing during rallies and political caravans. Two Capriles supporters were shot to death in the western state of Barinas last weekend.

Troops were dispatched across Venezuela to guard thousands of voting centers Sunday.

Chavez, who says he has emerged successfully from long treatment for cancer, held an impromptu news conference Saturday night, and when asked about the possibility of disputes over the vote, he said he expected both sides to accept the result.

"It's a mature, democratic country where the institutions work, where we have one of the best electoral systems in the world," Chavez told reporters at the presidential palace.

But he also said he hoped no one would try to use the vote to play a "destabilizing game." If they do, he said, "we'll be alert to neutralize them."

His opponents mounted a noisy protest in Caracas and other major cities on Saturday night, beating pots and pans from the windows of their homes to show displeasure with Chavez _ and also their hopes for change. Drivers on downtown streets honked horns, joining the din.

The 40-year-old Capriles, a wiry former governor affectionately called "Skinny" by supporters, infused the opposition with new optimism and opinion polls pointed to him giving Chavez his closest election.

Some recent polls gave Chavez a lead of about 10 percentage points, while others put the two candidates roughly even.

"Chavez is going to fight until his last breath. He doesn't know how to do anything else," said Antonio Padron, a bank employee backing the president.

Padron expressed optimism that the 58-year-old Chavez would win, noting the leader's survival of a fight with cancer that included surgery, chemotherapy and radiation treatment.

But Padron predicted a close finish: "It's a tough fight. The opposition has never been this strong."

Chavez won the last presidential vote in 2006 with 63 percent of the vote.

A former army paratroop commander first elected in 1999, Chavez has presided over an oil boom and has spent billions of dollars on government social programs ranging from cash benefits for single mothers to free education.

But he has suffered declining support due to one of the world's highest murder rates, 18 percent inflation, a deteriorating electrical grid and a bloated government accused of endemic corruption and mismanagement.

While his support has slipped at home, Chavez has also seen his international influence ebb since he emerged in the mid-2000s as leader of a like-minded club of newly elected Latin American leftist presidents.

"I want to tell President Chavez, I want to tell him his cycle is over," Capriles said at his final campaign rally Thursday.

Capriles says Chavez has stirred up hatred, hobbled the economy by expropriating private businesses and squandered oil wealth. He criticized Chavez's preferential deals supplying oil to allies, including one that lets Cuba pay with the services of Cuban doctors.

"We aren't going to finance the political model that exists in Cuba," Capriles said in a TV interview last week. "But we aren't going to break off relations with Cuba."

Chavez accumulated near-absolute power over the past decade thanks to his control of the National Assembly, friendly judges in the courts, and pliant institutions such as the Central Bank.

Gino Caso, an auto mechanic, said he would vote for Capriles because Chavez is power-hungry and out of touch with problems like 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."

Political analyst Ricardo Sucre said he expected the election to show "two halves, more or less even." Regardless of the result, he said, Venezuelans are likely to remain deeply divided by politics for years to come.

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Associated Press writers Christopher Toothaker and Jorge Rueda contributed to this report.

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Ian James on Twitter: http://twitter.com/ianjamesap