Iran's six presidential hopefuls staged last-minute election campaigning on Wednesday, hoping to woo millions of voters undecided between a slew of conservatives and a moderate cleric backed by reformists.
Momentum has built for cleric Hassan Rowhani, a former top nuclear negotiator, after the withdrawal of reformist Mohammad Reza Aref, and the endorsement of two former presidents, pro-reform Mohammad Khatami and pragmatist Akbar Hashemi Rafsanjani.
Rowhani, 64, faces stiff competition in Friday's election from the conservatives, especially hardline top nuclear negotiator Saeed Jalili, Tehran mayor Mohammad Baqer Qalibaf and ex-foreign minister Ali Akbar Velayati.
The three held separate campaign rallies in Tehran in the late afternoon, with none agreeing to step down to boost conservative chances.
According to an opinion poll published by Mehr news agency, Qalibaf was leading with 17.8 percent support from 10,000 voters canvassed, ahead of Rowhani with 14.6 percent.
Jalili followed with 9.8 percent.
The number of undecided voters in the survey stood at 30.5 percent -- translating to about 15 million voters -- while 11.3 percent declined to answer.
The surge of support for Rowhani came after Aref, the only reformist candidate, announced on Tuesday he was withdrawing at the urging of Khatami.
The former president subsequently asked voters "who seek the dignity and elevation of the nation" to vote for Rowhani.
But this does not mean reformists are united, according to Tehran-based analyst Mehdi Fazayeli.
"The way Mr Aref dropped his bid showed he was sad and annoyed. He did not name Rowhani in his farewell message... nor has (he) allocated his campaign resources to support Rowhani," Fazayeli told AFP.
Rafsanjani, a pillar of the 1979 Islamic revolution who himself was barred from running, has also backed Rowhani, saying he was "more suitable" for Iran's highest elected office than the other candidates.
The closing of reformist ranks behind Rowhani prompted the conservative camp on Wednesday to urge their candidates to coalesce.
Habibollah Asgaroladi, secretary general of a leading umbrella organisation for conservative groups, said without elaborating that consultations were under way to make "a coalition happen".
But any behind the scenes talks appear to have failed.
Jalili's campaign manager, Ali Bagheri, said his candidate would remain in the race "until the end".
"Jalili will make it to the second round should there be one," Bagheri told AFP.
Velayati, at a separate meeting in central Tehran, also vowed not to drop his bid.
Despite the reluctance of the conservative camp to rally behind a single candidate, Reza Marashi of the US-based National Iranian American Council advocacy group said this was vital for them.
"Unless the remaining conservative candidates coalesce, a splintered conservative field will face a candidate in Rowhani that has the backing of significant political and social forces in Iran," Marashi told AFP.
Wednesday is officially the last day of campaigning, but under Iran's electoral law, candidates and their supporters have until 8:00 am (0330 GMT) on Thursday, 24 hours before the polls open, to wind up their campaigns.
This year's campaign has been low-key compared with 2009 when boisterous rallies and street parties attracted crowds, as supporters of pro-reform candidates Mir Hossein Mousavi and Mehdi Karroubi faced off against conservative-minded incumbent Mahmoud Ahmadinejad.
The rallies turned into heated street protests when Ahmadinejad was declared winner for a second term, leading his opponents to allege massive electoral fraud.
Months-long demonstrations that followed turned deadly and were eventually crushed by the security forces. Mousavi and Karroubi were later placed under house arrest.
Some 50.5 million voters are eligible to vote for a successor to Ahmadinejad, under whose presidency Iran has been isolated internationally over its controversial nuclear drive.
Supreme leader Ayatollah Ali Khamenei, who has the final say on all key state issues, including nuclear activities, has urged a high turnout on Friday.
"If I insist on a massive turnout, it is because it will discourage the enemies (forcing) them to reduce the pressure and choose another path," he said on Wednesday.
Only eight male candidates out of nearly 700 registrants were approved by the hardline Guardians Council electoral watchdog. Two subsequently dropped their bids.
On Wednesday, the council stood by its decision to bar Rafsanjani, citing electoral laws.