* Chavez supporters show grainy video of Capriles aide
* Capriles sacks campaign official ahead of Oct. 7 vote
By Brian Ellsworth
CARACAS, Sept 13 (Reuters) - Venezuela's opposition presidential candidate Henrique Capriles kicked a top aide off his campaign on Thursday after vague corruption accusations by government leaders, shaking up his presidential bid just three weeks before the Oct. 7 vote.
Allies of socialist President Hugo Chavez showed a grainy video of Capriles aide Juan Carlos Caldera receiving cash they said could be used to finance Capriles' campaign or to pay bribes.
Caldera responded that he had received around $9,300 from a Venezuelan businessman who is known for close ties to Chavez.
The money was for his own campaign for mayor in municipal elections in December, Caldera said, adding the money was not for the Capriles campaign.
"We know this is a smear campaign; we will prevail," Caldera said during a press conference, saying he understood Capriles' decision to push him aside. "What this does it ratify the need to defeat this government."
The incident comes a day after several people were hurt when supporters of both sides fought and threw rocks ahead of a campaign stop by Capriles, heating up a campaign already marred by sporadic clashes and virulent insults.
It threatens to link Capriles with the OPEC nation's decades-long tradition of bribery and embezzlement of oil revenue just three weeks before the Oct. 7 election.
But the relatively small amount of money involved, as well as Capriles' swift response, will likely dampen the incident's impact on the opposition campaign.
Chavez leads the majority of the best-known polls, but they are notoriously controversial and divergent in Venezuela. One major firm has Capriles ahead.
The youthful former state governor has hoped to tap into public anger over alleged corruption by state officials. Chavez's critics and some of his disaffected supporters complain of seeing low-paid government officials driving fancy SUVs or taking lavish vacations.
In one famous 2007 incident, a businessman traveling to Argentina with Chavez's delegation was stopped at an airport carrying a briefcase with nearly $1 million in cash.
Caldera said he met several times with Venezuelan shipping magnate Wilmer Ruperti, who in 2002 and 2003 used his fleet to help Chavez defeat an opposition-led oil industry shutdown by importing fuel.
Caldera said Ruperti had approached him and expressed interest in meeting with Capriles. An assistant to Ruperti had given him the money and filmed the encounter with several cameras set up like a "television studio," Caldera said.
"I was too naive, I let myself get set up," he said.
Vice President Elias Jaua weighed in via his Twitter account: "The #corruptloser Capriles told Juan Carlos Caldera to go get his cash."
The new allegations mostly overshadowed accusations by a judge formerly allied with Chavez who wrote a letter made public on Thursday that gave a detailed account of how he was ordered to rig the trials of the president's adversaries.
Former Supreme Court Justice Eladio Aponte, who fled the country in April, wrote in a sworn statement that he acted on Chavez's orders to give 30-year sentences to police officers charged with involvement in a bungled 2002 coup.
"I don't pretend to exonerate my responsibility for what I did ... I simply wanted to rest my conscience," said Aponte, who says Chavez's office routinely interfered in cases.
According to U.S. intelligence sources, he is cooperating with U.S. authorities by providing details about the Venezuelan government's links to drug trafficking.
Aponte's comments will likely cement the belief within the opposition that Chavez uses the court system to his own benefit but is unlikely to become a major campaign issue.
Among the myriad polling companies in Venezuela, respected Datanalisis put Chavez ahead by 12 points in July, though Capriles' numbers have been creeping up and another well-known pollster, Consultores 21, has him neck-and-neck. Both sides disregard unfavorable polls and say their candidate is ahead.
A third term for Chavez would add another six years to Venezuela's experiment with socialism, characterized by price and currency controls, confrontation with business and frequent nationalizations.
Critics say the president has the upper hand in the election thanks to liberal spending of public funds to boost his image, and the use of state media to promote his campaign.
Capriles is promising a Brazil-style balance of free markets and social protection.
Investors believe he would bring a more market-friendly economy following 14 years of Chavez. But they also believe he could face potential unrest or protests by oil industry workers loyal to Chavez who could refuse to recognize his leadership.