With Chavez sidelined, opposition tests strength in Venezuela polls
* Capriles aims to cement role as opposition leader
* All eyes on Capriles-Jaua race in Miranda
* Chavez in delicate condition after surgery in Cuba
CARACAS, Dec 14 (Reuters) - Venezuelans vote for state governors on Sunday in an election that will decide if the opposition stays united behind youthful leader Henrique Capriles amid signs that President Hugo Chavez's cancer could force him to step down.
Capriles, the governor of Miranda state, lost to Chavez in the October presidential election but won 45 percent of the vote and is seen as the most likely candidate if Chavez is unable to stay in power and a new election is called.
Before that, however, he must defeat a challenge from a heavyweight Chavez protege in Miranda, the country's second-most populous state, to maintain his support among often-quarreling opposition parties.
Defeat for Capriles could prompt several opposition leaders to push their own claims to be the national opposition nominee at the next election. Any new fractures in the opposition would weaken its chances of victory.
"There are no automatic candidacies," cautioned Pedro Benitez of Democratic Action, one of the 20 or so politically diverse groups that make up the opposition coalition.
The opposition has seven of the country's 23 state governorships and is hoping to at least retain those on Sunday.
Campaigning has been completely overshadowed by Chavez's cancer operation in Cuba on Tuesday, his fourth in the last 18 months.
Officials have given grave assessments of the 58-year-old socialist leader's condition following the complex six-hour surgery. On Thursday they said doctors had to use "corrective measures" to stop unexpected bleeding that was a result of the procedure, but that his condition had since improved.
The overall showing of the opposition on Sunday will be an important indicator of its capacity to mobilize voters just two months after Capriles, a wiry and sports-loving lawyer by profession, was beaten by Chavez in October.
The headline race is in Miranda, where the government is trying to oust Capriles from the governor's office by backing Elias Jaua, a well-funded former vice president who was once a stone-throwing student radical.
"We are committed to making Chavez happy by showing him that Miranda was liberated from fascism and is being run by a socialist, by his son, which is what I am," Jaua told a rally.
If Capriles were to lose, local analysts say, it would be very unlikely that he would represent the opposition in a new presidential election.
Campaign events by the candidates of the ruling Socialist Party (PSUV) this week have turned into tearful vigils with supporters praying that Chavez recovers and can begin his new term on Jan. 10.
If Chavez has to step down, a new presidential election must be held within 30 days. He has named his vice president and foreign minister, Nicolas Maduro, as heir apparent in case he died or his illness forced him to give up office.
Other high-profile gubernatorial races on Sunday include the one in Aragua, where Chavez's former Interior Minister Tareck El Aissami is trying to win back the state for the PSUV. He was campaigning alongside Maduro on Thursday.
The vice president led the emotional crowd in a chant of "With Chavez and Tareck, we will win again!"
While the PSUV has displayed its powerful electoral machinery time after time over the years, the distressing news coming out of Havana has transfixed many distraught local party activists, perhaps taking the edge off its efficiency.
The fact the elections take place in mid-December could count against the opposition, many of whose middle-class supporters will have taken advantage of school holidays to travel abroad or within Venezuela for Christmas.
Elsewhere, Pablo Perez, who was runner-up to Capriles at the opposition's presidential primary vote in February, will be fighting to keep his post as governor in the oil-rich western state of Zulia.
In Lara state, Henri Falcon, a former military ally of Chavez who broke with him in 2010, is seeking re-election. And the president's elder brother Adan is campaigning for re-election in the family's home state of Barinas, in the central plains of Venezuela's agricultural heartland.
A good showing by the opposition would expand its power base, allow a new generation of leaders to gain crucial experience in office, and potentially give them leverage in putting the brakes on government policies at the local level.
A poor performance is likely to reopen some of the internal divisions that have plagued them in the past.
In the Oct. 7 presidential election, Chavez won the popular vote in all but two states - Merida and Tachira. But the opposition traditionally does better in local polls, where there is more emphasis on grassroots issues such as crime, failing services and infrastructure problems, than on Chavez himself.
"The country is full of problems that need resolving," Capriles told supporters in Miranda. "During the presidential campaign, so much was promised - now they have to fulfill that."
Opinion polls in Venezuela are notoriously diverse and controversial, and there have not been enough done to give a clear sense of how Sunday's vote will go. In Miranda, for example, one poll gave Capriles a lead of more than 20 percentage points, while another had Jaua 5 points ahead.
"Capriles should have the natural advantage for his experience, track record and high visibility," said Siobhan Morden, managing director at New York-based Jefferies & Co.
"However, there is debate on whether voters prefer the opposition candidate that knows the specific regional issues, or whether they prefer the official candidate for the connection to the resources of the federal government."
Should Capriles win on Sunday, and then face Maduro for the presidency if Chavez does not recover, he will benefit from the buzz he generated during the campaign earlier this year and the fact that his 45 percent share - 6.5 million votes - was the opposition's biggest against Chavez in a presidential election.
Though previous opinion polls say Capriles is much more popular than any of Chavez's allies, it could be an entirely different story against a Maduro candidacy that carried Chavez's blessing and the full power of the PSUV's electoral machinery.
"You wouldn't be comparing Capriles to Maduro, but Capriles to the emotion that would be created by such a loss" if Chavez were to die, said local political analyst Luis Vicente Leon. (Additional reporting by Marianna Parraga, Brian Ellsworth and Deisy Buitrago; Editing by Andrew Cawthorne, Kieran Murray and Mohammad Zargham)