Reza Khatami, the president's younger brother and a former member of parliament, is widely viewed as the strongest reformist candidate. But the public is deeply disillusioned with the reformers' failure to enact democratic changes, analysts say.
Plus, the Guardian Council disqualified Reza Khatami -- as well as more than 80 other reformist incumbents -- from running for parliament again in February elections, a move that diminishes the odds of winning approval to run for the presidency, analysts say.
Ali Akbar Hashemi Rafsanjani served as parliament speaker in the 1980s and as president from 1989 to 1997.
"The conservatives can win, but only by disqualifying all rivals. If they can, they will try to accept only people nobody knows," said Mohsen Mirdamadi, a former member of parliament and one of those disqualified from running.
A former parliamentary speaker, Mehdi Karrubi, and a former education minister, Mustafa Moin, are considered likely reformist candidates, politicians say.
Among conservatives, the other contenders so far are: Ali Akbar Velayati, a former foreign minister; Ali Larijani, a former state broadcasting chief; Mahmoud Ahmadi-Nejad, the mayor of Tehran; Gholam Ali Haddad-Adel, the speaker of parliament; Ahmad Tavakoli, a parliamentarian; and Mohsen Rezaie, a former Revolutionary Guards commander.
The most strident conservatives, who this year won the most seats in parliament, appear to prefer candidates other than Rafsanjani. "We believe the Expediency Council is a very suitable place for him," said Hossein Shariatmadari, a leading conservative thinker and editor of the Kayhan newspaper.
Rafsanjani's biggest obstacle may be his record. "I haven't met anyone who says anything good about him," a Western diplomat who monitors Iranian politics said on condition of anonymity.
Rafsanjani's brother, Hashemi, said initial polls strongly favored the former president. "In the last poll, he had about 60 percent -- with a big gap between him and the next, who had 10 or 11 percent," he said.
Iran, however, is traditionally fickle about its politicians. On the eve of the reformers' victory eight years ago, the conservative candidate was expected sweep to victory.
"Sometimes the polls are wrong," Hashemi conceded. "It's doesn't happen only in the U.S."