* Maduro seen as moderate but faithful socialist disciple
* "We are the children of Chavez"
* Investors hope for more pragmatic leadership
By Brian Ellsworth
CARACAS, Dec 12 (Reuters) - After rising from bus driver to union leader to vice president of Venezuela, Nicolas Maduro could soon be at the helm of the South American OPEC nation if a third bout of cancer pulls President Hugo Chavez out of office.
Anointed as the former soldier's successor, Maduro is the most popular of Chavez's inner circle and the most qualified to carry on his oil-financed socialism.
Maduro, who is seen as a moderate who has developed alliances around the world during six years a s foreign minister, would assume power if Chavez has to step aside. He would then have to run as the Socialist Party's candidate in an election against the opposition.
Because he has stuck so closely to Chavez's official line, it is difficult to know what Maduro's policies might be if he were leading the country on his own.
His experience as a union leader taught Maduro the importance of dialogue, suggesting he could begin mending fences with business leaders and the opposition after a decade of hostility.
But he will face intense pressure from ideological radicals and self-interested profiteers who h ave enriched themselves under Chavez's government to extend the state's grip over the economy and private enterprise.
Maduro's first speech after being named successor indicated he is likely to assume Chavez's blustering rhetoric while presenting himself as a disciple of the cancer-stricken leader.
"We are eternally grateful to Chavez ... we will be loyal to Chavez beyond this lifetime," a tearful Maduro said during a rally for state governors in a speech in which he invoked independence heroes, shouted triumphant slogans and then lowered his voice for dramatic effect in hallmark Chavez style.
"We are the children of Chavez."
For the first time since his 2011 diagnosis for an unspecified type of cancer, Chavez has suggested his illness could keep him from continuing his 14-year self-styled revolution. O n Tuesday he underwent his fourth operation for cancer after twice declaring himself completely cured.
The possible transition generated optimism for a more moderate government after years of intransigent socialism.
Wall Street investors drawn to Venezuela's highly traded bonds, as well as oil companies seeking greater access to the world's largest crude reserves, are watching closely.
Maduro survived Chavez's mercurial micro-management and became one of the longest-lasting ministers in the frequently rotating Cabinet by executing orders and repeating anti-U.S. rhetoric around the world.
He often appeared as a towering sidekick over Chavez's shoulder in television broadcasts.
In 1992, when Chavez was jailed for a failed coup that made him famous, Maduro took to the streets to demand his release alongside his partner Cilia Flores, who led the legal team that helped get Chavez freed within two years.
Maduro and Flores are considered a "power couple" in Chavez's government.
Maduro gained notoriety as a rabble-rousing legislator during the tumultuous early years of Chavez's rule. He was at the front lines of efforts to defeat a failed coup and a crippling oil strike in 2002 and a recall referendum in 2004.
Upon rising to head of Congress, Maduro swapped the blue jeans and plaid shirts of a union leader for sharp suits. Even in his high-toned attire, he still could be seen elbowing through reporters to get to the appetizer table before presidential press conferences.
As foreign minister, Maduro has trotted the globe denouncing U.S. foreign policy and cultivating allies in emerging markets such as Russia and China, which would become a key financier.
One of Maduro's offices includes a large portrait of the late Indian spiritual guru Sai Baba, who he and Flores, who also is a former head of Congress, visited in 2005.
Maduro has often been at Chavez's side during his cancer treatments in Havana.
"Nicolas is a person who can talk to anyone," said Jose Albornoz, who worked alongside him as a legislator for a party allied with the government that later split with Chavez.
"His work with unions taught him to communicate with his adversary. I think he could open a dialogue with (opposition leaders) to make sure his government is successful."
Maduro could face tough economic decisions including a widely expected currency devaluation, a price hike for heavily subsidized fuel and cuts in state spending after Chavez's lavish campaign that helped him win re-election in October.
The idea of transition from Chavez to Maduro may well have come from Cuba's Fidel Castro, Chavez's political mentor who six years ago handed over power to his younger brother Raul after falling ill himself. The younger Castro has since begun a slow transition away from centrally planned communism.
More pragmatic leadership from Maduro could help tackle problems including crime, inflation and unemployment that critics say have gone unchecked because of Chavez's rigid ideological approach to them.
While Chavez has a reputation for choosing government officials on the basis of loyalty and political views, people who have worked with Maduro commend him for prioritizing credentials and hard work.
"He's a real man of the people," Ecuadorean Ambassador Ramon Torres told Reuters.