An extremely conservative cleric is being inaugurated as president of Iran on Thursday.

The cleric, Ebrahim Raisi, won a June election that had disqualified any potential rivals. Critics said Mr. Raisi’s victory had been engineered to reflect the choice of his mentor and ally, Iran’s supreme leader, Ayatollah Ali Khamenei.

The election called attention to the role of Iran’s president in a system of governance dominated by clerical leaders since the Islamic revolution that overthrew the American-backed monarchy more than four decades ago.

Although the system contains some checks and balances, power has been increasingly concentrated in the hands of the supreme leader, who under Iran’s Constitution has more authority than the president.

Here’s a closer look at the president, and the powers he does — and doesn’t — possess.

Until last month, Mr. Raisi, 60, was the head of Iran’s judiciary. He spent much of his career as a prosecutor and is on a U.S. sanctions list over his human rights record. In 1988, he sat on a committee that sent about 5,000 imprisoned government opponents to their deaths, according to human-rights organizations.

He is a protégé of Mr. Khamenei, 82, who is largely responsible for Mr. Raisi’s ascendance. They share a deep suspicion of the West in general and antipathy toward the United States in particular. Mr. Raisi is believed to be Mr. Khamenei’s main choice to succeed him.