The polls have opened in Iran for a presidential runoff vote in which a relative newcomer on the national scene is seeking an upset win over a political veteran.

One week after voting in the first round, Iranians again headed for the polls Friday to choose a president.

Ali Akbar Hashemi Rafsanjani, who served as president from 1989 to 1997, is facing the mayor of Tehran, Mahmood Ahmadinejad, to replace outgoing reformist president Mohammad Khatami. The two men moved to a runoff contest after none of the seven candidates permitted to run in the first round won outright.

Karim Sadjapour, a Tehran-based analyst with the International Crisis Group, which monitors world developments, says voters - especially ardent pro-reform ones - who saw their favorites pushed out in the first round face what may be unpalatable choices.

"There are people on both sides of the spectrum who are actually wary of seeing either man become president, and they may have to make a choice of the lesser of two evils," said Karim Sadjapour.

Mahmoud Ahmadinejad
Mr. Rafsanjani has positioned himself as a moderate and pragmatist, talking of increased political and economic liberalization. But Mr. Ahmadinejad, a hardline conservative and Revolutionary Guard veteran, has mounted a surprisingly strong challenge with a populist message aimed at the economically disadvantaged. He has promised to institute monthly stipends for citizens.

The first round was unusually bitter. Charges of voting irregularities came from losing reformist candidates who claimed Mr. Ahmadinejad received illegal help from a paramilitary militia arm of the Revolutionary Guard. On Thursday, the Interior Ministry announced the arrests of 26 people for violating election laws, but did not identify them.

The runoff campaign has been bitter as well. The Ahmadinejad camp has tried to portray Mr. Rafsanjani as a typical old guard politician. Mr. Rafsanjani's supporters have painted Mr. Ahmadinejad as an extremist who will try to roll back the incremental social and political reforms won under President Khatami's tenure.

Final results should be known sometime Saturday.