Iran holds a landmark presidential election Friday amid warnings of violence if the vote is rigged to secure President Mahmoud Ahmadinejad’s return.

As the most tumultuous campaign in the Islamic Republic’s 30-year history drew to a close, Mir Hossein Mousavi, the incumbent’s strongest challenger, appealed to Ayatollah Ali Khamenei, the Iranian Supreme Leader, to ensure that the election was fair.

Those close to Mousavi went further, claiming that Ahmadinejad could win only by cheating — and that this could spark riots and chaos on the streets.

Click here for photos.

Saeed Laylaz, a political consultant, said he feared a "Tiananmen Square-style experience," with the military moving in to crush any protests.

Such warnings were lent credence by Yadollah Javani, a leader of the hard-line Republican Guard, who has vowed to suppress any attempt by Mousavi’s reformist supporters to mount a “velvet revolution” after the election.

Officials expect a near-record turnout of the 46 million eligible voters after an extraordinary campaign marked by vast rallies, all-night revelry on the streets of Tehran and unprecedented infighting among the Iranian political elite.

Until recently, Ahmadinejad’s re-election looked all but certain, but urban middle-class Iranians began to rally behind Mousavi, a former prime minister and relative moderate.

Continue reading at the Times of London.