The 47-year-old Jalili has been Iran's chief nuclear negotiator since 2007. He is also a special representative of the supreme leader.
Jalili represents the second generation of Islamic revolutionaries, and lost his leg during the Iran-Iraq War.
At one point, Jalili was said to have had the backing of ultraconservative cleric Ayatollah Mohammad Taghi Mesbah Yazdi, who is regarded as outgoing President Mahmud Ahmadinejad's spiritual adviser.
Jalili also appears to have Supreme Leader Khamenei's trust.
Jalili, who began his career as a diplomat in the 1990s, is a hard-liner who also received veiled endorsements from prominent figures within Iran's powerful Islamic Revolutionary Guards Corps (IRGC).