Early Life
Ali Khamenei began his studies of Shiite Islam at an early age and under the guidance of some of the time periods most prominent scholars, including future revolutionary leader Ruhollah Khomeini, who he would become closely aquatinted with later in his life. Starting from 1963, Khamenei joined the anti-Shah Mohammed Palhavi protests that were building throughout Iran. Between 1963 and 1979 Khamenei was arrested several times by the Shah's secret police, but unlike many Iranian revolutionary leaders he never fled the country. After the Iranian Revolution's success in 1979 he joined Khomeini in starting the new Islamic Republic of Iran, and was quickly appointed to the revolutionary council. He would also become the deputy minister of defense and a negotiator in the U.S. embassy hostage crisis (Britannica Khamenei 2019).
Presidency
In 1981, following the impeachment of Abolhassan Banisadr, Khamenei began his campaign for president. He was elected with the majority of the vote in 1981, and later re-elected in 1985. But at the time the Iranian president had very little power, and was a more symbolic post. Although he attempted to nominate many conservatives to government positions, the parliament was further left leaning than he was and rejected the majority of his nominations. This lead to him and his appointed prime minister Mir Hossein Mousavi disagreeing on many things and often getting into bitter arguments (Britannica Khamenei 2019).
Time as Supreme Leader
By the year 1989, Ruhollah Khomeini's health was declining quickly, but it was unclear who would be fit to replace him as the supreme leader. Ali Khamenei was Khomeini's preferred choice, but he didn't meet the qualifications of being a senior cleric. In order to make way for Khomeini's successor, he adjusted the constitution to allow for less strict standards to become the supreme leader. Khomeini died months after making this change and Ali Khamenei became the second supreme leader of Iran (Britannica Khamenei 2019). Khamenei did not have the vast media support or the overall popularity of his predecessor, but due to Khomeini's support the assembly of experts appointed him. He has generally remained neutral throughout his time as supreme leader, with the exception of expressing support for Mohammed Ahmadinejad in his bid for the presidency. His support for the conservative candidate is often credited to his victory in both 2005 and 2009. Although he supported him in his campaign, Khamenei and Ahmadinejad often feuded. Ahmadinejad's presidency was the first time a supreme leader ever reverted a presidents economic decision. It is possible that Khamenei may revert another decision in the future due to the increased pressure put on Iran by the U.S. during Hassan Rouhani's presidency and the protests against him.
Historical Significance
Ali Khameini has served as the highest leader in Iran since 1989, and as a result has made many decisions that have impacted the country. Although his views and actions aren't particularly different from his predecessor, him continuing Khomeini's policies has lead Iran in a continually Anti-American and conservative direction. Several actions during his leadership, such as the endorsement of Ahmadinejad, appointments to the assembly of experts, and economic decisions have affected and continue to affect Iran today.