A coalition of reformists, technocrats and traditionalist conservatives is lining up behind Akbar Hashemi Rafsanjani as he prepares for tomorrow's presidential election run-off. His supporters are warning that a victory for Mahmoud Ahmadinejad, the mayor of Tehran, will lead to a military government.
"Go and vote. Otherwise they are going to make an Iranian Taliban here," the defeated reformist Mehdi Karroubi said in support of Mr Rafsanjani.
The reformists believe the Islamic Revolutionary Guards Corps and the Islamic Basij militia have been planning to take power since early in Mohammad Khatami's presidency - and have gradually staged an takeover of the system.
They say the two units have illegally mobilised support for Mr Ahmadinejad, who was a special forces operative with the guards and a Basij instructor.
"I first warned of a military class in the political scene three years ago," Mashallah Shamsolvaezin, a journalist, said. "First they won the municipal elections, then they took control of the Majlis [parliament] and the third step is to take the executive."
Conservatives scorn such claims and point to an apparently genuine rise in support for populist right-wingers among the working class. They contend that Iranian society has undergone a backlash against the inefficiency of reformist rule and the growing wealth inequalities of recent years. They portray tomorrow's run-off as a battle between the hard-working poor and the corrupt, easy-living rich.
The Basij were formed during the war with Iraq. With its regular army immobilised through desertion, purges and equipment shortages, Iran was forced to mobilise its citizens into a militia to defend against an Iraqi invasion.
The Basij today has hundreds of thousands of members and the Guard Corps, which receives the best equipment Iran has to offer, numbers 150,000.
"They model themselves on Pakistan, where political power is dominated by the military," Mohammed Atrianfar , a close aide of Mr Rafsanjani, said. "They have interfered before, but never in a presidential race."
Ebrahim Yazdi, head of the dissident Freedom Movement and former foreign minister, said: "The military wants more power like it does anywhere in the world.But their justification is that during the war with Iraq, they defended Iran's integrity and now think they have the right to denounce the government's deviation from pure Islamic values."
When Mr Khatami took Iran by surprise with a landslide victory in 1997, conservatives began to worry. When students rioted across the country two years later, they believed the Islamic system was in peril and 29 guardsmen wrote to Khatami all but threatening a coup.
"There is a danger of militarisation, if not a military takeover," Anoush Ehteshami, head of the school of government and international affairs at Durham University, said.
"The exchanges that followed the student riots between the president, his allies and the guards were indicative of the rise of the military as a direct result of the reform process."
Now reformists and centrists alike fear a more militant government, which might curtail social and political freedoms at home, while pursuing a nationalistic line abroad.
Even those who will boycott tomorrow's poll are warning against the danger of a fundamentalist win. "We think the establishment has the will to put a military person at the head of the executive," Abdullah Momeni, a student leader, said. "But it will cause an atmosphere of fear and extremism."Reuse content