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Fernando Llano, Associated Press
Opposition presidential candidate Henrique Capriles speaks during a news conference at his office in Caracas, Venezuela, Monday March 26, 2012. Capriles will face Venezuela's President Hugo Chavez in presidential elections in October.

CARACAS, Venezuela — President Hugo Chavez has a double-digit lead over the opposition's presidential candidate, but a quarter of Venezuelan voters haven't committed to either candidate, a poll said Thursday.

The survey released by the Caracas polling firm Datanalisis said nearly 45 percent of those polled said they would vote for Chavez, while 31 percent supported Miranda state Gov. Henrique Capriles. About 25 percent were undecided.

"Those undecided ones are going to indicate the trend in the future," said Luis Vicente Leon, the polling firm's president.

Chavez, who has been in office since 1999, is seeking another six-year term in the Oct. 7 election.

The survey questioned about 1,300 people in Venezuela between Feb. 29 and March 7, and had a margin of error of nearly 3 percentage points, Leon said.

He said the percentage of people expressing no choice for a candidate had increased since the firm's previous poll a month earlier, when almost 50 percent said they would vote for Chavez and 35 percent backed Capriles.

Leon said the monthly poll is paid for by about 300 clients that include both private businesses and state companies as well as individuals. He said some of the clients include political leaders, but he didn't identify them.

About 62 percent of respondents said they viewed Chavez's performance favorably, compared to 50 percent who had a favorable view of Capriles' performance as governor.

Poll results have varied widely in Venezuela recently, with each political camp touting dueling figures. Government media have reported on polls indicating Chavez is ahead of Capriles by as much as 30 points. Last week, the polling firm Consultores 21 released a survey indicating Chavez and Capriles are running head-to-head.

Chavez appeared on state television early Thursday after returning home from a five-day round of radiation therapy in Cuba, where he has been undergoing cancer treatment.

"Thanks to God, I've withstood the treatment very well," Chavez said. "Let's hope that's the case next time."

He said that the radiation treatments had been administered for five days in a row and that he would be in Venezuela until Saturday, when he plans to return to Havana for the next round.

Chavez has said the radiation therapy is intended to prevent any new cancer threat after a surgery last month that removed a second tumor from his pelvic region. He had another tumor removed from the same location in an earlier operation in June.

The 57-year-old leftist president has vowed to overcome cancer and win the October vote.

Capriles, 39, won a February primary vote to become the opposition's only candidate. Capriles says he favors social programs for the poor but also criticizes Chavez's expropriations of private business and says if elected he will seek to encourage private investment to create jobs.

Capriles has also focused some of his recent criticism on rampant violent crime, which Venezuelans view as the country's top problem, according to recent polls.

"Every year, the violence has gone up," Capriles told reporters on Thursday. "In any country in the world, the first one who's responsible is the head of state."