Determined to protect a dominant security role and vast economic interests, Iran's Revolutionary Guards military force is quietly backing a hardliner in May 19 presidential polls, with an eye toward a bigger prize: the succession of the supreme leader.

President Hassan Rouhani, a relative moderate elected in 2013 in a landslide on promises to open up Iranian society and reduce its international isolation, is widely seen as the favorite to win a second term next week.

But the Islamic Revolutionary Guards Corps (IRGC), and the Basij, a volunteer militia under the Guards' command, are taking steps to promote the candidacy of his main rival, hardline cleric Ebrahim Raisi.