IRAN’S LAST presidential election four years ago offered hope of real change in its theocratic regime, through the reformist Green movement. But if the race to elect a replacement to Mahmoud Ahmadinejad alters anything, it may be for the worse — at least from the West’s point of view. Scarred by the popular uprising of 2009, the country’s supreme leader, Ayatollah Ali Khamenei, has ensured that only conservative regime loyalists were allowed to enter Friday’s first round of elections. His favorite may be Saeed Jalili, a slavish follower who as Iran’s nuclear negotiator has prided himself on his inflexibility. Though some of the five other candidates are slightly more independent, all have made a point of saying that all authority over foreign policy will lie with the ayatollah.

Who could be worse than Mr. Ahmadinejad? The populist demagogue regularly caused international sensation by denying the Holocaust and pledging to wipe Israel from the map. But he never came close to acting on his rhetoric, and the backlash made it easier for the United States to win support for international sanctions. Mr. Ahmadinejad also tried to build his own power base, and he appeared to favor a diplomatic deal limiting Iran’s uranium enrichment — until he was blocked by Mr. Khamenei. His successor may well offer the world a more pragmatic face while posing less of a challenge to the supreme leader’s intransigence.

One such personage would be Mohammad Bagher Ghalibaf, Tehran’s mayor and a former Revolutionary Guard commander who has led in some polls. Mr. Ghalibaf, 51, has been regarded as a good city manager and portrays himself as someone who can rescue the country’s economy from the recession brought on by sanctions. In meetings with Western leaders, he has conveyed more concern with Iran’s national interests than with Islamic ideology. But he would be a fervent supporter of the Guard’s aggressive agenda, which has included intervention in Syria’s civil war and the staging of terrorist attacks in foreign capitals.

In a televised debate last week, three other candidates, including former foreign minister Ali Akbar Velayati and former nuclear negotiator Hassan Rouhani, lambasted Mr. Jalili’s handling of nuclear negotiations with a six-nation international coalition. But their point seemed to be that a more polished approach could have avoided sanctions, not that the drive for a bomb should be compromised. Mr. Rouhani, who has emerged as the default candidate of Iran’s reformists, will not be allowed to win.

The nuclear negotiations have been on hold for the past two months, after a failure to make progress; the elections have given the United States and its partners reason to avoid drawing conclusions about whether a diplomatic solution is still possible. As Iran continues to enrich uranium and install a new generation of advanced centrifuges, however, the window for a settlement grows steadily smaller. Once a new president is place, the Obama administration should demand a clear response from Tehran on whether it is willing to curb its program — and be prepared for a negative answer.