Iranian President Hassan Rouhani. (Behrouz Mehri/Agence France-Presse via Getty Images)

IRAN’S PRESIDENTIAL election on Friday is a familiar contest between a relative moderate, the incumbent Hassan Rouhani, and a hard-line conservative backed by the Revolutionary Guard and, it seems, Supreme Leader Ayatollah Ali Khamenei. It’s not correct to say the difference between them is insignificant: Mr. Rouhani, embraced by Iran’s educated middle class, favors more relaxed enforcement of Islamic rule at home and engagement with Western investors abroad, while opponent Ebrahim Raisi is a populist who rails against foreign influence and predicts the “Zionist regime” of Israel will be “wiped . . . from Jerusalem.”

From the U.S. point of view, however, it’s not clear that there’s a side to root for in what will be the 12th presidential election since the 1979 revolution. Both candidates have promised to stick with the 2015 deal that froze Iran’s production of enriched uranium and other nuclear activities for about a decade. And both appear committed to Iran’s aggressive bid for hegemony in the Middle East by other means, including military interventions in Iraq and Syria, support for rebels in Yemen and harassment of U.S. ships in the Persian Gulf.

Mr. Rouhani’s bet has been that Iran can wage those wars while simultaneously boosting its economy with lucrative investment and trade deals. So far he’s been half-right: Iran has doubled its oil exports since the nuclear deal, boosting economic growth to more than 7 percent. But big Western banks and investors have largely stayed out of Tehran, in part because of lingering U.S. sanctions. The government has consequently been unable to finance big infrastructure projects, and ordinary Iranians have seen few benefits. Unemployment remains stuck at more than 12 percent.

The president has meanwhile had no luck reining in the judiciary or Revolutionary Guard at home. At least four U.S. citizens, along with several other Westerners, are being held as de facto hostages by these factions, further depressing the appetite of would-be investors. Though he has been endorsed by the leaders of the 2009 Green Movement, Mr. Rouhani failed to deliver on his promise to have those leaders released from years of house arrest.

The 2009 uprising was triggered by the apparent ma­nipu­la­tion of a presidential election. This year, Iranians appear unlikely to surge into the streets even if Mr. Khamenei fixes the vote in order to install Mr. Raisi, who is rumored to be a potential successor to the 77-year-old supreme leader. Mr. Rouhani does not offer genuine democratic change and thus lacks the popular support garnered by 2009 candidate Mir Hossein Mousavi or former president Mohammad Khatami.

Some observers of Iran calculate that the West would be better off with a victory by Mr. Raisi, who would likely return Iran to international isolation and fuel domestic discontent. The nuclear deal was essentially a bet by the United States that Iran would change over a decade and lose its appetite to pursue nuclear weapons. The Obama administration supposed that the kind of economic opening promoted by Mr. Rouhani would bring about that change. But real transformation in Iran will require a collapse of the Islamic Republic. A victory by Mr. Raisi would frustrate Iranians hoping for change in the short term, but maybe bring a reckoning for the regime closer.