Iranians headed to the polls on Friday in a highly scrutinized presidential election that pits hardline leader Mahmoud Ahmadinejad against reformist candidate Mir Hossein Mousavi.
An estimated 45,000 polling stations opened nationwide Friday morning. State television encouraged people to vote and broadcast video footage of past elections, nationalistic songs and pictures of Iranians fighting against Iraq in the 1980-88 war.
Supreme Leader Ayatollah Ali Khamenei cast his ballot minutes after the polls opened, as is customary at presidential elections. He urged voters to get out and vote early.
"As far as I see and hear, passion and motivation is very high among people," said Khamenei. "We expect people at packed polling stations to be able to choose the best choice for heading the executive branch for four years."
The rowdy campaign reached a crescendo in the past few days with duelling rallies by supporters of Ahmadinejad and Mousavi, that drew tens of thousands into the streets of Tehran. Fervent, youthful supporters of Mousavi accused the president of undermining Iran's international standing with his confrontational style and of devastating the economy.
Possible runoff
There are four candidates in the running вЂ" former Revolutionary Guard commander Mohsen Razai and former parliamentary Speaker Mehdi Karroubi trail the leading two candidates. The winning candidate has to secure more than 50 per cent of the vote, which many analysts say is unlikely in the first round of voting.
If none of the candidates can secure this margin, a runoff election between the top two vote-getters will be held on June 19. Consequently, the support of the two trailing candidates could be crucial to the frontrunners. Razai is expected to draw conservative voters, and Karroubi has a largely moderate base.
Ahmadinejad, meanwhile, has broad support among rural and working poor voters, while Mousavi has much of the middle-class and urban vote.
Mousavi looks to be mounting a strong challenge to Ahmadinejad, whose once high approval ratings have flagged as a sinking economy drags down his popularity with it. Mousavi has the backing of former president Mohamed Khatami, who was elected in 1997 and 2001.
Mousavi has criticized Ahmadinejad's foreign policies as provocative, and says he will seek to better Iran's relationship with the international community, particularly with its neighbours in the Middle East and the United States. U.S. President Barack Obama has spoken of improving ties with the Islamic nation.
All candidates are in favour of continuing Iran's national nuclear program, which has given many citizens a sense of national pride. None of the candidates recognize Israel as a nation.
Regardless of who wins, the outcome is expected to have at best a modest impact on issues like the nuclear development program and foreign policy at large.
As supreme leader, Khamenei has the final word on all state matters, as mandated since 1979's Islamic revolution. But analysts say he may show flexibility if there is broad public support for a moderate agenda.
Still, the president has influence over some domestic affairs, such as the economy, and serves as Iran's highest-ranking envoy on the international stage.
Sudden surge
Political scientist Sadegh Zibakalam told CBC's Margaret Evans he finds it hard to explain the surge in support for Mousavi, Iran's prime minister from 1980 to 1988. Mousavi has maintained a low profile in recent years.
"Who knows him to begin with? The man has been prime minister [but] during the past 20 years no one's heard of him."
But he believes Mousavi's challenge may be too strong for Ahmadinejad to withstand.
"It appears that an earthquake, a flood, an avalanche is coming that is much more powerful than the one that brought Khatami to power.
"We are surprised, we are baffled, but it is coming."
With files from The Associated Press