ISTANBUL • A burgeoning crisis between Iran and the United States has threatened to undermine the pragmatic Iranian President Hassan Rouhani, who was elected four years ago on promises to end the country's isolation from the West.
But now, amid new tensions with the Trump administration, Mr Rouhani's pro-dialogue approach is under attack. The shift - from detente with the former Obama administration to open hostility with the White House under President Donald Trump - has left Mr Rouhani particularly vulnerable as he gears up for a presidential vote in May.
In the few weeks since Mr Trump took office, the two sides have sparred over Iran's ballistic missile programme, the ban on Iranian nationals entering the US and new White House sanctions targeting Iran's weapons systems.
Mr Trump's then national security adviser, Mr Michael Flynn, announced that the US was putting Iran "on notice" over its ballistic missile tests, which the White House said defied a United Nations Security Council resolution. Iran responded with more military exercises and a threat to "rain down" missiles on its enemies.
"The conventional wisdom is that if the US really begins to crack down - to put Iran on the defence, keep it under threat, and take away some benefits - it will work against Rouhani," said Mr Gary Sick, who was the principal White House aide on Iran during the 1979 revolution and subsequent holding of US Embassy personnel as hostages.
Iran's conservatives have yet to field a viable candidate to oppose Mr Rouhani, said Mr Sick, who is now a research scholar at Columbia University's Middle East Institute. But in Iranian election campaigns, which last just a few weeks, "things happen very fast", he said.
Mr Rouhani, a cleric turned politician, has the political advantage of an incumbent. And, despite disagreements over policy and ideology, he appears to still have the support of Supreme Leader Ayatollah Ali Khamenei, whose broad power can make or break candidates.
Mr Khamenei recently nudged Mr Rouhani's chief rival - former president and right-wing firebrand Mahmoud Ahmadinejad - out of the race, after rumours swirled of a dramatic political comeback.
Given the uncertainty and the Trump administration's more hawkish policies, Iran's election, scheduled for May 19, "will not be an easy one for Mr Rouhani", said Mr Abas Aslani, world news editor at Iran's Tasnim News Agency. Iran's Guardian Council, a clerical oversight body, will vet the contenders and announce the approved candidates in late April.