TEHRAN, Iran — Iranians began voting Friday in the country’s first presidential election since its nuclear deal with world powers, as incumbent Hassan Rouhani faced a staunch challenge from a hard-line opponent over his outreach to the wider world.

The election is largely viewed as a referendum on the 68-year-old cleric’s more moderate policies, which paved the way for the nuclear accord despite opposition from hard-liners.

Economic issues also will be on the minds of Iran’s over 56 million eligible voters as they head to more than 63,000 polling places across the country. The average Iranian has yet to see the benefits of the deal, which saw Iran limit its contested nuclear program in exchange for the lifting of some sanctions.

In the election, Rouhani has history on his side. No incumbent president has failed to win re-election since 1981, when Ayatollah Ali Khamenei, the current supreme leader and most powerful man in Iran, became president himself.

That doesn’t mean it will be easy, however. Rouhani faces three challengers, the strongest among them hard-line cleric Ebrahim Raisi, 56.

Raisi, a law professor and former prosecutor who heads an influential religious charitable foundation with vast business holdings, is seen by many as close to Khamenei. Raisi has even been discussed as a possible successor to him, though Khamenei has stopped short of endorsing anyone.

Raisi won the support of two major clerical bodies and promised to boost welfare payments to the poor. His populist posture, anti-corruption rhetoric and get-tough reputation — bolstered by his alleged role condemning inmates to death during Iran’s 1988 mass execution of thousands of political prisoners — are likely to energize conservative rural and working-class voters.

Mostafa Hashemitaba, a pro-reform figure who previously ran for president in 2001, and Mostafa Mirsalim, a former culture minister, also remain in the race.

Voting is scheduled to run until 6 p.m., though Iranian authorities routinely extend voting for several hours in elections.