After nearly a year of cancer treatment that has forced President Hugo Chavez to step back from the spotlight, a burly former bus driver with a dark mustache and affable smile is emerging more than ever as the president's stand-in.

In recent weeks, Foreign Minister Nicolas Maduro has led news conferences, touted a new labor law and criticized the U.S. government with gusto. He even rallied a crowd of supporters while wearing a track suit emblazoned with the yellow, blue and red of Venezuela's flag, just like one Chavez sometimes wears.

Maduro's prominence is generating speculation that he could be a leading candidate to succeed the president, or at least represent him during grueling campaign events, if Chavez's health fails ahead of Venezuela's Oct. 7 presidential election.

Chavez has built his 13-year-old presidency around his own larger-than-life persona and hasn't anointed a successor, instead pledging to recover from cancer treatment and once again return to the front line of his campaign. Nonetheless, Maduro's role as government spokesman has grown in the past month, and his regular appearances at Chavez's side have many thinking he has received the presidential nod.

"I think the best-trained politician Chavez has is Nicolas Maduro," said former diplomat Vladimir Villegas, a journalist who hosts a Venezuelan radio program.

Villegas said Maduro seems to outshine Vice President Elias Jaua with his experience on the international stage, his ties to labor groups and his close relationship with Cuba's government. Maduro has been the country's top diplomat since 2006.

Speaking with confidence, Maduro took to championing a newly approved labor law before government supporters earlier this month, while the president was receiving cancer treatment in Cuba.

"With our commander Chavez, today Venezuela is at the vanguard, ahead in the fight for a new humankind, for another humankind, for a new world," Maduro said. "That world is being built here, and that world has one single name: socialism of the 21st century."

While heaping praise on Maduro, the president likes to note that critics once derided his foreign minister as a simpleton because of his working-class roots, which included a stint as a union leader for workers in the Caracas Metro subway system.

Chavez's close friendship with Maduro goes back to the 1980s, when the leftist president was an army officer and formed a clandestine movement that eventually carried out a failed coup attempt in 1992.

In his youth, Maduro belonged to a small political group called the Socialist League and traveled to Cuba for training in union organizing. To this day, Maduro is considered by some observers the aide with the closest links to the Cuban government within Chavez's inner circle.

Maduro has such a close relationship with Chavez that he seems to know how the president comes down on just about any issue. At the same time, he has proved adept at speaking on Chavez's behalf without getting ahead of his boss' public statements. Chavez likes to joke with Maduro that he eats excessively, quipping that the foreign minister should cut back on the submarine sandwiches that he likes to devour.

Maduro's other longstanding relationship is with partner Cilia Flores, who is the country's attorney general and former National Assembly president.

A year after Chavez took office in 1999, Maduro was elected to the National Assembly and then rose through party ranks to become the body's president before being named foreign minister.

Maduro, 49, brushed aside the possibility of becoming Chavez's successor when asked by The Associated Press during a recent pro-government demonstration, saying it's "a joke by a defeated right wing that lives only for intrigue."

The crowd at that May 1 demonstration cheered and applauded enthusiastically for Maduro as he stepped onto a stage alongside other leaders of Chavez's United Socialist Party of Venezuela, a warm welcome surpassed the response for others on the stage, such as National Assembly President Diosdado Cabello. Some red-clad supporters even shouted greetings from nearby buildings and pressed close to shake his hand and hug him.

Asked about his connection with the crowd, Maduro said, "Chavez is more applauded."

A survey in March by the Venezuelan polling firm Datanalisis found that Maduro ranked among the most popular figures in Chavez's movement after the president himself. Maduro, with 20-percent support, nearly matched Jaua, for whom 23 percent said they would vote if they had the choice. Other leaders of Chavez's movement trailed far behind in the single digits. The poll consulted 1,300 people and had a margin of error of less than 3 percentage points.

Chavez himself has maintained a lead in recent polls over opposition presidential candidate Henrique Capriles, a 39-year-old state governor.

Looking at the field of possible successors, the investment bank Barclays Capital said this month that while Maduro could face a "difficult challenge" against Capriles, that scenario would also depend on the public sympathy that could well up if Chavez were to pull out of the race.

Opposition lawmaker Ismael Garcia, who formerly supported the government, said he doubts that Maduro would have "sufficient weight to lead a process in Venezuela and face elections." He said Chavez's supporters are first and foremost with the president, but wouldn't necessarily be in Maduro's camp.

Luis Gallardo, a Metro employee who stood watching television with other government supporters in a downtown Caracas plaza, said he worked with Maduro years ago and thought the foreign minister has since gained enormous political savvy.

"I think he's a good card that Chavez has there ... who's clear about the aims of the revolution, the aims of El Comandante," Gallardo said.

Compared with other Chavez aides, Gallardo said, "I see Nicolas Maduro as more combative, more the Chavez style. He calls a spade a spade. He's not maintaining an appearance, above all when I see him make comments against the empire, against the United States, all that."

Chavez "has been training people, and I think among them are Nicolas Maduro and Elias Jaua," he said.

Carlos Mora, another government supporter in the plaza, said he doesn't think Maduro or anyone else could adequately replace Chavez.

"He's the natural leader because he has the charisma," Mora said, referring to Chavez. He said Maduro is "a person who doesn't have that charisma, who doesn't reach the people."

Chavez has kept Venezuelans guessing about his intentions while he has undergone two cancer surgeries, chemotherapy and most recently radiation therapy treatments.

Rumors of a possible political transition have grown in the Venezuelan news media and on the streets after Chavez last month began naming close allies to a new Council of State, which under the constitution advises the president and is led by the vice president.

Maduro has been frequently at Chavez's side in Cuba and joined the president's relatives during informal chats. Maduro was even shown on television last month playing bocce ball in Cuba with Chavez and the president's elder brother, Adan.

What remains unclear is whether the foreign minister would continue Chavez's radical approach or moderate the government line if he were called upon to replace Chavez, Villegas said.

"It would have to be seen whether Maduro with Chavez is the same as Maduro without Chavez," he said.