Former reformist President Mohammad Khatami urged Iranian voters in an online video to reelect President Hassan Rohani on May 19.
Khatami, who was the country's president from 1997 until 2005, has since been banned from any appearances in Iranian media by the country’s hard-line judiciary.
"Mr. Rohani's government has been a successful one, despite all the limitations, problems, and the great expectations," Khatami said in the video.
"We should all go and vote for Rohani, for freedom in thought, logic in dialogue, law in action, securing the rights of citizens, and enforcing social and economic justice," he added.
Rohani is seeking a second four-year term. He is currently facing five rivals, but some could withdraw in favor of more prominent candidates.
The president is viewed as the "moderate" choice and many see the election as something of a referendum on the policies that led to a landmark deal with international powers that saw Tehran curb its nuclear program in exchange for some sanctions relief.
Despite the media ban, Khatami has been active through social media to support pro-reform candidates.
"We have started on a path with Rohani and we have come halfway,” he said. "We have resolved some problems and bigger problems remain for us to resolve on this difficult path with him."
Based on reporting by Reuters, AP, and AFP