Supreme Leader
Ali Khamanei, the current Iranian Supreme Leader has established his reputation as a hardliner, particularly after his role in blocking many of the attempts for reform made by former President Khatami, Ahmadinejad’s predecessor. With the power to approve candidates running for the election, as well as the ability to curtail legislation and mobilize the Revolutionary Guard and other paramilitary forces, the Supreme Leader is the true power center within Iran.

Shrouded in secrecy, Khamanei keeps his preferences unknown to a large extent, though rumors regarding his relationship with President Ahmadinejad are rife. Many claim the relationship between the two men has been strained at times, with Khamanei unhappy at some of Ahmadinejad’s more explosive rhetoric.

The Presidency
The highest elected official in Iran and head of the executive branch, the President does have a large role in formulating policies and running Iran – as long as the Supreme Leader agrees.

Mahmoud Ahmadinejad
President of Iran since 2005, this former mayor of Tehran and former commander in the Revolutionary Guard has become infamous for his denial of the holocaust and fiery rhetoric on the world stage. Within Iran, Ahmadinejad commands much support amongst the rural poor, who see him as a common man.

Supported by fellow conservatives, Ahmadinejad has sought to revive Iran’s role as a revolutionary state, after the reforms attempted by his predecessor. He has stepped up Iranian support for militant groups in Iraq and Lebanon as well as work on Iran’s nuclear program, all moves that have angered much of the international community.

In the 2005 election Ahmadinejad was viewed as a relative novice and surprised many – reportedly including Iran’s Supreme Leader – when he managed to win in the second round. Opponents claim his win was dependent on a large part to support – and possibly rigging – by the Basij, a hardline paramilitary force that works with the Revolutionary Guard.

Mir Hossein Mousavi
Mousavi, who served as Prime Minister during Iran's 1980-88 war with neighboring Iraq and is seen as Ahmadinejad's main challenger. He has accused the president of squandering a surge in oil revenues and advocates better ties with the West, but rejects demands that Tehran halt sensitive nuclear work, Reuters say.

While his long years away from the political stage mean few young voters can remember his premiership, he has picked up significant youth support as the leading reformist candidate. Backed by former Presidents Khatami and Rafsanjani, both of whom are very popular amongst reformers, the former amateur artist and specialist in Islamic architecture is expected to present a formidable challenge to the hard-line incumbent.

His campaign, according to the Associated Press, has used internet resources as well as youth networks to engage and mobilize many of Iran’s disenchanted youth, who form a core of his base.

Mehdi Karroubi
A former speaker of the Iranian Parliament, and cleric, Mehdi Karroubi is also a leading reformist candidate, campaigning on the need to bring change to Iran. With views similar to that of Mousavi, Karroubi has also criticized Ahmadinjead’s handling of Iran, though he enjoys much less support than the other reform candidate, Mir Hossein Mousavi.

Enjoying greater support amongst in the rural areas, Karroubi is expected to take many of the reformist votes from Mousavi, according to AP, but is not expected to make it to the second round run-off.

Mohsen Rezai
This former economist and current Secretary of the Expediency Council — a governmental body tasked with advising the Supreme Leader and liaising with the Iranian parliament is significantly more conservative than Mousavi and Karroubi. Especially critical of Ahmadinejad’s handling of the Iranian economy — which has seen rising unemployment and inflation — Rezai has made economic affairs the center of his campaign.

As with Karroubi, though AP reports it is likely Rezai will chip away at many of Ahmadinejad’s more conservative supporters, he is not expected to gain enough votes to make it to the June 19th run-off vote.