TEHRAN — The decision on Tuesday to bar the presidential candidacy of Ali Akbar Hashemi Rafsanjani, a founding father of the revolution and a former president, shocked Iranians, particularly those among the 70 percent of the population that is under 35 and grew up when he served in many leading positions.

“They say a revolution eats its children,” said Mehdi, 27, a teacher. “But in the case of Rafsanjani, the revolution has eaten its father.”

The exclusion of Mr. Rafsanjani and another thorn in the conservatives’ side, Esfandiar Rahim Mashaei, could foreshadow even greater repercussions, analysts and commentators said.

Since its founding in 1979, the Islamic republic has been characterized by constant and often public competition among opposing power centers, a back-and-forth that gives ordinary citizens and private business owners the ability to navigate among the groups.