It will see an election not only for the Iranian parliament, but also for the 86-seat Assembly of Experts, the body responsible for choosing and supervising the supreme leader.
The contest for the succession heated up this week when the Assembly of Experts unexpectedly chose Ayatollah Mohammad Yazdi, the 83-year-old former judiciary chief, as its chairman rather than Ayatollah Mahmoud Hashemi Shahroudi, previously seen as the favorite of Khamenei.
Candidates are also vetted by the Council of Guardians, six of whose 12 members are appointed by the supreme leader, suggesting one way in which Khamenei may influence his own succession.
Some in Tehran believe Khamenei revealed a preference for his successor four years ago when he delegated to Ayatollah Shahroudi his own constitutional role of mediation between parliament, president and judiciary.
Shahroudi had taken over as acting chair of the Assembly of Experts after Ayatollah Mohammad Reza Mahdavi-Kani fell into a coma in June before his death in October.
At 66, Shahroudi remains younger than Yazdi, and with any succession to Khamenei perhaps many years off, the succession remains very uncertain.
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