Hassan Rouhani receives endorsement ahead of Iran election

A reformist candidate dropped out of Iran's presidential election on Tuesday and threw his support behind President Hassan Rouhani, in a widely expected move that will strengthen the incumbent's campaign against a hard-liner.

Eshaq Jahangiri, senior vice-president under Rouhani, dropped out, leaving just four candidates in the race. "I will dedicate all my abilities to support Rouhani" in Friday's election, Jahangiri said in a statement.

Rouhani also has the support of former President Mohammad Khatami, another reformist, who endorsed him on Sunday.

On Monday, Tehran Mayor Mohammad Bagher Qalibaf dropped out of the election to back hard-liner Ebrahim Raisi. The two campaigned together on Tuesday, appearing at a packed rally in Tehran, where Raisi promised Qalibaf an important role in his administration.

The election is largely viewed as a referendum on the nuclear deal struck with world powers and shepherded by Rouhani's administration. Iran agreed to limit its enrichment of uranium in exchange for the lifting of some economic sanctions.

Iran has since resumed crucial oil exports to Europe and concluded billion-dollar deals to purchase passenger planes, but the effects have yet to trickle down to most Iranians, creating an opening for hard-liners, who feel Rouhani gave too much away.

Raisi is believed to be the favourite of Supreme Leader Ayatollah Ali Khamenei, who will remain Iran's top decision-maker, but it's unclear whether Raisi will be able to unseat Rouhani. Every Iranian president since 1981 has won re-election.

Iranian elections are overseen by a clerical body that vets candidates and bars anyone seen as posing a challenge to Iran's unique brand of theocratic rule.