MEXICO CITY — “It’s absolutely illusory to think that (President Hugo Chavez) may return to exercise a post that is so exhausting as leading a country in modern times,” Heinz Dieterich said Friday in an interview at his office at a Mexico City university.

Dieterich, a German sociologist and ideologue, said a succession battle already is playing out within Chavez’s socialist party.

A leftist thinker, Dieterich invented a slogan he called “Socialism for the 21st Century,” which was adopted by Chavez. The two met in 1999, nurturing a friendship over debates at Miraflores Palace in Caracas. Dieterich never received a salary or occupied a formal post as an adviser to Chavez, and he said he hasn’t spoken to the president since 2005.

But he is generally acknowledged to be part of the leftist brain trust around the former army paratroop commander and remains in contact with high-level officials in Venezuela’s government, including current governors and military commanders.

He’s also a frequent visitor to Cuba, where Chavez is fighting recurring cancer, internal bleeding and a severe lung infection after undergoing his fourth cancer surgery on Dec. 11. With Chavez unseen in public since and officials of his government offering grim assessments of his health, Venezuela’s National Assembly meets Saturday to plot what to do if Chavez cannot be sworn in for a fourth term on Thursday — something analysts say is a near certainty.

Dieterich said he believes that once Chavez passes from the scene, Venezuelans will be led by a more collective form of government, a vast change from Chavez’s domineering tactics that used slang-laced oratory and a showy populist style to win the support of Venezuela’s poor in the years since Chavez took power in 1999.

Chavez’s handpicked successor, Vice President Nicolas Maduro, doesn’t have the political chops to govern in the same fashion, Dieterich said, but will maintain many of the same policies as Chavez, including full support for Cuba, although he may seek a thaw in chilly relations with Washington.

“Maduro will have to turn over more power to the ministries and to his team,” Dieterich said. “I believe that we will see the politics of a more conventional, bourgeois government of Latin America.”

Maduro faces a rival within the ruling United Socialist Party of Venezuela but appears to have gotten the upper hand over Diosdado Cabello, a high-profile former army officer who has held numerous posts under Chavez, most recently as the National Assembly president, a position that he may regain on Saturday.

Under one scenario, if Chavez cannot be inaugurated Thursday, Cabello would take over the presidential office and call elections within 30 days. Cabello last month suggested that Chavez’s inauguration could be postponed, a move that some in his party viewed as a transparent grab for time to elbow out Maduro.

“By exposing himself with this maneuver, he lost a lot of power,” Dieterich said of Cabello. “The armed forces saw that he didn’t want to carry out the express public wishes of the president ... and they obviously decided to make clear that Chavez’s wishes would prevail.”

Maduro said Friday that Chavez could be sworn in by the Supreme Court later on if he’s not able to take the oath of office next week before lawmakers.