Rafsanjani, a 75-year-old power broker who tells foreign visitors he was the father of Iran's ballistic missile programme, is the unofficial leader of the faction opposing Ayatollah Ali Khamenei, the supreme leader. He quietly provided much of the money and organisation behind Mir Hussain Mousavi's campaign.
In the other corner, the Ayatollah himself has consistently championed President Mahmoud Ahmadinejad. "The elites are extremely divided," said Professor Ali Ansari, an Iran specialist at St Andrews University. "The hardliners are trying to reshape the Islamic Republic in their own image and this has created very serious divisions."
Rafsanjani may oppose the hardliners, but that does not make him a reformer. Born in 1934 in Kerman province, he was part of the regime's inner circle from the moment that Shah Reza Pahlavi was toppled in the 1979 Revolution. Rafsanjani became Speaker of parliament and, almost exactly 20 years ago, he was instrumental in ensuring Ayatollah Khamenei became Supreme Leader.
This was no mean feat: The new Supreme Leader lacked religious scholarship and was hastily promoted to become an Ayatollah.
Rafsanjani's reward was to become president, a job he held until 1997. During this period, he concentrated on burnishing his own business interests and reviving Iran's economy after the shattering war with Iraq. This focus on domestic recovery, and self enrichment, earned him a reputation as a pragmatist.
Rafsanjani also proved to be without scruples. In 1994, Iranian-backed terrorists bombed a Jewish centre in Buenos Aires, killing 84 people. After an investigation, Argentina indicted Rafsanjani, alleging responsibility, although Interpol did not support an arrest warrant.
After leaving office in 1997, Rafsanjani became chairman of the Expediency Council, a body that mediates between the different arms of the regime. But he made powerful enemies. Ahmadinejad regarded his wealth with distaste and viewed him as a living betrayal of the revolution's principles.
In 2005, Rafsanjani tried to return as president, only to be defeated in the election by Ahmadinejad, who benefited from the Supreme Leader's open support. This rift between Rafsanjani and Ayatollah Khamenei therefore became the key division in the regime.
