"Here I am, and every day, I feel in better physical condition," the president said. " And I firmly believe, that that expression about physical limitations that you used, it's not going to be a factor in this campaign."
Crafting a youthful image is also important because Chavez is 18 years older than his political rival, who turned 40 over the summer.
"Venezuelans are looking for a new way," Capriles has told his supporters. "It's been 14 years of the same government. This government has already completed its cycle and has nothing more to offer. They're only recycling promises."
Chavez, presumably because of his health, has not held as many rallies or traveled as often as he has in previous campaigns. His re-election effort has been mostly through presidential addresses that state-run television stations are mandated to carry.
Chavez would have been unable to run for re-election this year because of constitutional limits. But his United Socialist Party of Venezuela pushed for a referendum in 2009 in which voters eliminated term limits. Winning another term in office next month would allow Chavez to rule Venezuela until 2019, the 20th anniversary of his rise to power.
Whatever his health condition, Chavez remains a force in Venezuelan politics. His likeness is everywhere -- on television, on huge banners and the radio.
His popularity remains high among Venezuelans, and his supporters remain as ardent as ever. However, Capriles has been constantly on the road, and his supporters say the momentum is shifting.
"We see it everyday, people are opening up their doors and inviting us in," said Tomas Guanipa, secretary-general of Capriles' Justice First party.
With high stakes, accusations fly
The campaign has heated up in the final stretch, with accusations of improprieties flying back and forth.
In the past month, the Capriles' campaign has accused Chavez of using a televised presidential address to bump an opposition campaign event from the airwaves. And the Chavez campaign released hidden-camera footage that purportedly showed one of Capriles' campaign leaders accepting a bribe.
"There are definitely moments of tension," said Welsch, the retired professor at Universidad Simon Bolivar.
That tension has also erupted into violence at several campaign rallies. On Saturday, gunmen reportedly killed three pro-Capriles activists in the western Venezuelan state of Barinas. Earlier this month, in the port city of Puerto Cabello, a group of people identified as Chavez supporters -- also known as "Chavistas" -- threw rocks as Capriles made his way to a campaign rally. Several people were injured in an ensuing clash between the two sides.
Capriles' Justice First party has accused the ruling party of harassment during the campaign, particularly when the Chavez campaign released a hidden-camera video showing a lawmaker working on Capriles' campaign accepting cash from a businessman. Chavez's campaign said the money purportedly was a bribe for his opponents campaign and accused the Capriles camp of financing itself in this way.
Capriles responded to the video by firing the lawmaker and joining in the government's call for an investigation.
"It's a very difficult environment we are campaigning in," said Guanipa of Capriles' Justice First party.
He characterized the harassment of the opposition campaign as acts of desperation from the ruling party.
"It's the agenda of someone who is defeated," he said.
Representatives from Chavez's campaign declined to comment, but Chavez told reporters last week that a Capriles victory was impossible, citing polls.
"We are ready for the will of the people to be respected and for no one to come and disrespect the Venezuelan will," Chavez said.
Meanwhile, a former minister and vice president under Chavez, Jose Vicente Rangel, accused the opposition of being capable of a coup or economic sabotage, if they lose.
The back-and-forth accusations can only mean one thing, according to analyst Sagarzazu: "All the shenanigans that have been happening point in the direction that the government knows that things are close."
The biggest question mark for observers abroad is whether the election will bring instability to Venezuela no matter who wins.
Former U.S. ambassador to Venezuela, Patrick Duddy, said unrest is not inevitable, but in an analysis for the Council of Foreign Affairs, laid out several scenarios of concern, beginning with the fact that "Chavez and several of his most senior associates have asserted that there will be instability and violence if he is not re-elected."
Violence could break out if it appears Chavez is going to lose, if he dies unexpectedly or if he wins with the appearance of cheating, Duddy wrote.