Since Ayatollah Khamenei is 77 years old and is rumored to be in poor health, the Assembly of Experts may soon play a key role in shaping Iran's future, and it's likely that Iran's moderates had hoped Rafsanjani would once again wield considerable influence in that process.
He was a widely known figure and veteran of Iranian politics, having been president for eight years from 1987.
Ayatollah Hashemi Rafsanjani was rushed to the Tajreesh Martyres Hospital in Northern Tehran after experiencing a heart failure Sunday afternoon.
Rafsanjani was said to be still an influential figure in Iran.
At the time of his death, he was chairman of the Expediency Council, a political consultative body tasked with resolving disputes between parliament and the Guardian Council, a watchdog comprised of hard-line clerics and jurists.
But his political allegiances later shifted towards reformists, especially after a rift grew between him and Khamenei over the 2009 disputed presidential elections. Rafsanjani also served as president of Iran from 1989 to 1997.
Speaking after authorities had launched a crackdown that killed some of those who protested against Ahmadinejad's contested poll victory, Rafsanjani condemned the use of lethal force.
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"Today, operating through various foundations and front companies, the family is also believed to control one of Iran's biggest oil engineering companies, a plant assembling Daewoo automobiles, and Iran's best private airline (though the Rafsanjanis insist they do not own these assets)".
Rafsanjani, center, arrives to register his candidacy for the 2013 presidential election at the interior ministry in Tehran.
He was a man known for a sharp wit but who could also be ruthless. In 2003, Rafsanjani was listed among Iran's "millionaire mullahs" by Forbes magazine.
Rafsanjani made another bid for the presidency in 2005, but ultimately lost to hardliner Mahmoud Ahmadinejad.
This explains why Mr Rouhani was the first top official to attend the hospital where Mr Rafsanjani died. In 2015, one of his sons was sentenced to a 10-year prison term on embezzlement and security charges.
I pray from deep in my heart for Divine blessings, mercy and forgiveness for him and express my condolences to his esteemed wife, his children and brothers and other relatives.