Hundreds of thousands of backers of opposition candidate Henrique Capriles thronged the streets of the Venezuelan capital, echoing his rising threat to President Hugo Chavez's reelection.

"I want to thank you all. Because I think this is the biggest rally Caracas has ever seen," glowed Capriles, 40, to the massive crowd on Sunday as he wrapped up his campaign not far from the presidential palace.

Supporters roared: "You see it; you feel it: President Capriles!"

"Look at that mass of people; Chavez is screwed now," one young man shouted. "Why does he think he can be president for his whole life anyway?"

The telegenic former governor of Miranda state has compared himself to David fighting Goliath.

Venezuelan opposition presidential candidate Henrique Capriles arrives to a campaign rally in Caracas, on September 30. Hundreds of thousands of backers of Capriles thronged the streets of the Venezuelan capital, echoing his rising threat to President Hugo Chavez's reelection.

And he hopes he can emulate the Bible story of the boy who felled the mighty giant before becoming king of Israel.

"I ask you, the Venezuelan people, to judge: who is part of the process of change. And who was sickened by power, clung to it and deceived the Venezuelan people?" an emotional Capriles shouted.

After breezing through past elections, Chavez entered the last week of campaigning against a rival who has gained ground in opinion polls.

The leftist leader, in power for almost 14 years, is vying for a fourth term in office that would extend his presidency by another six years, but Capriles wants a major upset on October 7.

Chavez, who used the country's oil wealth to reduce poverty, brushed aside his last rival in 2006 by taking almost 63 percent of the vote.

The latest opinion poll gives the 58-year-old incumbent a 10-point advantage over Capriles, but the young challenger has cut the lead by half in just four months.

Chavez was favored by 49.4 percent of voters compared to 39 percent for Capriles in a poll released this week by Datanalisis. A significant number of voters, 11.6 percent, remain undecided.

Other polls gave Chavez a bigger lead, while some found a statistical tie.

"All the big polling firms show a narrowing gap and a significant increase in voter intentions in favor of the opposition leader," said Datanalisis president Luis Vicente Leon.

Supporters attend a campaign rally by Venezuelan President Hugo Chavez in Monagas, northeastern Venezuela. Chavez, in power since 1999, has easily won the last three presidential elections, and the latest poll shows the leftist leader holding a 10-point lead over opposition candidate Henrique Capriles. Duration: 00:39

But Chavez, who declared victory over cancer in July, has voiced confidence that he would win re-election and use the next term to make his socialist revolution permanent.

"They know that they are losing, that the gap is irreversible," Chavez told thousands of supporters at a recent rally in the western state of Falcon, where people danced to the election song "Chavez, Heart of the People."

True to his provocative style, Chavez has derided his rival as a "loser" and a "political illiterate" who would bring chaos to Venezuela.

Chavez said he believed he had beaten cancer and would be strong enough to rule for another six years if he scores another term.

Venezuelan President Hugo Chavez waves to supporters during a campaign rally in Cabimas, on September 30. The leftist leader, in power for almost 14 years, is vying for a fourth term in office that would extend his presidency by another six years, but opposition candidate Henrique Capriles hopes to pull a major upset on October 7.

"I think so, I feel great," he told AFP when asked if he had fully recovered from his illness.

"If I didn't feel strong enough, I wouldn't be here. We're even going to work at a faster pace."

With Chavez dominating the public airwaves, Capriles has taken a page out of the president's own playbook by bringing his campaign directly to the people, going door to door to meet with ordinary Venezuelans.

Capriles, who campaigns with a baseball cap in Venezuela's colors, has sought to bring a fresh face to the opposition, which has been associated with an old system of parties that shared power for 40 years until Chavez's rise.

"We must defeat Goliath, and each one of you is David. I am David, but each one of you is David too," he told a recent rally that played his own campaign song, "There is a Path."

Capriles has seized on the country's high murder rate -- 50 homicides per 100,000 inhabitants in 2011 -- to criticize the president's handling of the country's crime wave.

While the government accuses him of conducting a US-style "marketing" campaign, the center-left Capriles promises to improve the lot of Venezuelans by maintaining and revamping many of Chavez's socialist programs.

Despite the opposition candidate's rise in opinion polls, political analyst Farith Fraija noted that the president continues to count on "hardcore Chavez voters who give him a comfortable edge of more than 10 points."

Capriles, for his part, has to rely on "unpredictable" undecided voters to have any hope of winning, Fraija said.