On a hot summer afternoon, three main conservative candidates on Wednesday refused to drop their individual Iranian presidential election bids despite pressure to coalesce against the moderate reformist-backed candidate.
One of the three, top nuclear negotiator Saeed Jalili, spoke to a crowd of devout religious supporters, touting his record of resisting the demands of the international community seeking to curtail Iran's atomic drive.
"We are behind enemy lines," joked the 47-year-old war veteran, alluding to a stand-off with the West over Iranian uranium enrichment that has resulted in painful economic sanctions against Tehran.
"Iranians should not fall into the trap of doubt set by the enemy," he said, provoking chants of "Death to those who advocate compromise!"
Jalili represents supreme leader Ayatollah Ali Khamenei in talks with world powers that have so far failed to produce a breakthrough.
Iran insists its nuclear drive is peaceful, rejecting Western fears that it is aimed at developing a military nuclear capability.
The parents of Mostafa Ahmadi Roshan, a nuclear engineer killed in a bombing in January 2012, attended the Jalili rally.
"We gave what we hold most dear for the nuclear energy programme... We will not compromise it," Ahmadi Roshan's mother said.
Calls within the conservative camp for Jalili to step down are increasing, but these were firmly rejected by his campaign manager, Ali Bagheri.
"Jalili will remain until the end. Do not pay attention to opinion polls. Jalili will make it to the second round should there be one," Bagheri told AFP.
A couple kilometres (miles) away, Palestine Square was packed with thousands of supporters of Tehran Mayor Mohammad Baqer Qalibaf, chanting that "he is the man of action".
"We should not allow mismanagement to take away the future of the youth," said Qalibaf, also a war veteran, of the economic policies of President Mahmoud Ahmadinejad's administration in facing up to sanctions imposed because of Iran's nuclear drive.
Qalibaf, 51, is considered another leading candidate among the conservatives, and he has vowed to repair Iran's ailing economy in "two years".
His record as a national police chief and Tehran mayor, coupled with his loyalty to Khamenei, has led to his political stock rising in recent years.
Qalibaf did not give any hint as to whether he would consider joining with other conservatives to increase their chances against Hassan Rowhani, a former nuclear negotiator who enjoys the support of reformists and moderates.
Rowhani on Tuesday received endorsements from two ex-presidents, pro-reform Mohammad Khatami and pragmatist Akbar Hashemi Rafsanjani, after the withdrawal from the race of the sole reformist, Mohammad Reza Aref.
The third campaign rally on Wednesday was by supporters of Ali Akbar Velayati in central Tehran.
Around 5,000 people in an indoor volleyball stadium brandished Iranian flags, posters and banners in support of Velayati, who told the crowd he would improve Iran's relations with the world should he be elected.
Addressing reports that he was being urged by conservatives to drop his presidential bid, Velayati said: "Despite all the rumours, I will remain in the race until the end."
A middle-aged man in the crowd who did not give his name said why he supported Velayati.
"We don't want a mayor and we don't want a commander. We need a veteran diplomat who knows how to lift the sanctions," he said.