The fate of the world in the next year might well hinge on a 72-year-old cleric who has never traveled outside his country and who lives a secluded life in Tehran. Whether Iran will make a deal with the international community or choose defiance — whether Iran will face an Israeli strike — will depend on the moods and wishes of Ayatullah Ali Khamenei. He is the second man to run the Islamic Republic, after Ayatullah Ruhollah Khomeini. His authority derives from religion in a formal sense, but he is a savvy political player. He was the Deputy Defense Minister under Khomeini and outmaneuvered more-liberal clerics to move into the position he now holds. He has bested all his foes. Ultimately, however, the system he presides over could prove to be unstable. International pressures mount, and domestic discontent remains high. Khamenei is the Supreme Leader, but given that he is also the Middle East's longest-serving dictator, one wonders whether he will also be Iran's last Supreme Leader.
Zakaria is an editor-at-large for TIME and the host of Fareed Zakaria GPS on CNN