Iran is to ban physically weak candidates from next month's presidential election, seen as a way of excluding a former leader who is a threat to hard-liners.
Ex-president Akbar Hashemi Rafsanjani's entry in the race upset calculations because of his popularity, reputation and potential to draw voters away from conservatives.
Mr Rafsanjani is 78. Opponents claim that he is too old to run the country, and the body that must decide who can run in the June 14 election indicated it agrees - as a way of removing the threat to Iran's hard-liners.
Abbas Ali Kadkhodaei, spokesman of the Guardian Council that vets election candidates, said the council will not allow candidates who are limited in their physical abilities."If a person is able to work only few hours a day, it's natural that he can't be approved," he said.
The unexpected entry of Mr Rafsanjani into the race has cut into chances of victory for a candidate loyal to Iran's Supreme Leader Ayatollah Ali Khamenei in the June 14 vote. There is also widespread speculation in Iranian media that Esfandiar Rahim Mashaei, president Mahmoud Ahmadinejad's close confidant, will be barred from running.
Mr Ahmadinejad cannot run for another term as president according to limits under Iran's constitution. Instead, he has been trying to ensure that a loyalist succeeds him.
Hard-liners accuse Mr Mashaei of being the leader of a "deviant current" that seeks to undermine Islamic rule and compromise the Islamic system. Some critics have even claimed he conjured black magic spells to fog Mr Ahmadinejad's mind.
Given Mr Mashaei's role in a messy power struggle he is likely to be barred, but Mr Rafsanjani is seen as too respected to be disqualified. He is a founder of the 1979 Islamic revolution that brought the clerics to power. He was the closest confident of Ayatollah Ruhollah Khomeini, spiritual leader of the 1979 revolution. Even Mr Khamenei largely owes his position to Mr Rafsanjani's support.
A government crackdown in 2009 put an end to street protests, but Mr Rafsanjani remained critical over the way the ruling system dealt with the crisis.
Political analyst Saeed Leilaz said the organised campaign to discredit Mr Rafsanjani reflects hard-liner concerns over his electoral strength. "They are shouting because their candidates can't beat Rafsanjani. If Rafsanjani is weak and doesn't enjoy popular support, why are they so angry?" he said.