Opinion | As Islamism Fades, Iran Goes Nationalist

The election of Donald Trump, followed by his withdrawal from the nuclear deal and renewed American sanctions against Iran, has brought Mr. Rouhani’s reformist momentum to a halt. Instead, a sense of betrayal by the United States and of a threat to the country’s territorial integrity appears to be emerging among Iranians.

Iranian hard-liners have sensed the beginning of a change in the popular mood. Two weeks ago, Kayhan, a daily newspaper known for its close ties to the supreme leader and the Revolutionary Guards, declared “The End of the Western Illusion” as “the greatest achievement” of the last Persian year, which ended on March 20. Iranian elites who once galvanized society and received votes with the promise of better relations with the United States now simply repeat the angry anti-American rhetoric of their conservative rivals.

These days, Javad Zarif, Iran’s once-smiling foreign minister and the chief nuclear negotiator, sounds more like the former hard-line president Mahmoud Ahmadinejad. Even Ali Akbar Salehi, the M.I.T.-educated head of the Atomic Energy Organization of Iran and nuclear negotiator, recently said that everyone from the proponents to the opponents of the regime “and from the revolutionaries to the anti-revolutionaries have come to believe that the United States is our enemy.”

In taking away Iran’s nuclear leverage, reimposing the sanctions and heavily arming its regional rivals, the United States has intensified anxieties about national security in the republic. Consequently, a national security discourse that brings the elites and the masses together is being constructed, and the Trump administration is providing credibility for it.

The Islamic Republic of Iran has survived not just because of its security apparatus but also because its leaders have been able to manage public sentiments and intra-elite conflicts. And Iran’s leaders have found that President Trump’s hostility toward Iran is helping to rally otherwise resentful citizens behind the regime and create a new cohesive Islamist-nationalist ideology.

This could have a demobilizing effect on Iran’s underground but still vibrant civil society and further boost the Revolutionary Guards’ influence over foreign policy. There is less and less popular and elite opposition to Mr. Khamenei’s claim that if the Revolutionary Guards did not fight terrorists in Damascus, it would be fighting them in Tehran. It is likely that many will consider investment in the regime an investment in their own and their homeland’s security. What was once considered regime security is increasingly seen as national security.

For four decades, the American and Iranian governments have simultaneously pursued a system of reward and punishment against Iranian citizens for opposite goals. Washington has hoped to foment public uprisings leading to regime change; Tehran has sought compliance and regime durability.