The candidates are: incumbent President Hassan Rohani, a reformist; conservative cleric and former prosecutor Ebrahim Raisi; Tehran Mayor and former police chief Mohammad Baqer Qalibaf; reformist First Vice President Eshaq Jahangiri, a Rohani ally; conservative former Culture Minister Mostafa Mirsalim; and former Iranian National Olympic Committee head Mostafa Hashemitaba, a centrist.

Here is a picture of the stage with the six candidates.

A little reminder of where Iran stands economically in the region, at least according to the 2016 indicators as cited by The World Bank:

Iran is the second largest economy in the Middle East and North Africa (MENA) region after Saudi Arabia, with an estimated Gross Domestic Product (GDP) in 2016 of US$412.2 billion. It also has the second largest population of the region after Egypt, with an estimated 78.8 million people in 2015. Iran’s economy is characterized by the hydrocarbon sector, agriculture and services sectors, and a noticeable state presence in manufacturing and financial services. Iran ranks second in the world in natural gas reserves and fourth in proven crude oil reserves. Economic activity and government revenues still depend to a large extent on oil revenues and therefore remain volatile.

Candidates are on the stage, listening to the Koran reading. The debate will start any minute now.

The debates are key to building public interest in the vote. They’re held on Fridays -- the weekend in Iran --so that people have time to watch them. The first live televised debates were held in 2009, generating great interest among Iranians.

Here's a quick glimpse at the six candidates in today's debate. They are the last candidates standing after the Guardians Council reviewed around 1,600 applications -- reportedly including just a couple dozen serious aspirants -- for the ballot.

Profiles: Six Still Standing In Race For Iran's Presidency

All six candidates are sitting in a back room awaiting the start of the debate. Nervous?!

Ahead of the May 19 vote, Iran has blocked Instagram live video feature, the semi-official ILNA news agency reports. Iran's hard-line judiciary last week blocked calls on the highly popular messaging app Telegram.

Farzan Sabet, a nuclear security fellow at Stanford University and managing editor of a website, IranPolitik.com, has a look at the three main candidates: