Iran's President Ebrahim Raisi chairs a cabinet meeting in Tehran, Aug. 8.

Photo: -/Agence France-Presse/Getty Images

This was the week that the optimistic case for restoring the 2015 Iran nuclear deal died. Like so many other innocents, it died at the hands of Ebrahim Raisi, the hanging judge handpicked by Iran’s supreme leader to guide the Islamic Republic through the Biden years.

For Iran optimists, the goal of the Joint Comprehensive Plan of Action was not only the normalization of U.S.-Iranian relations but the normalization of Iran. Ending sanctions and restoring economic relations between the Islamic Republic and the rest of the world would reduce the influence of hard-liners over the Iranian economy. Ending Iran’s political isolation would undermine the radicals’ argument that unrelenting foreign hostility justifies harsh crackdowns at home. All this would open a political window for moderates, who would increasingly soften the regime’s harsh policies at home and end its confrontation with neighbors. A nonnuclear Iran would become a stable, democratic force in the Middle East, optimists believed.

But Supreme Leader Ali Khamenei has no intention of ending up like Mikhail Gorbachev. By ruthlessly engineering the election of a hard-liner’s hard-liner to the presidency, Mr. Khamenei has slammed the door on normalization and nailed it shut.

That’s only one of the problems afflicting the JCPOA. Instead of welcoming the Biden administration’s eagerness to return to President Obama’s Iran policy, Tehran has turned up its nose at American attempts to chart a course back to mutual compliance with the terms of the deal. The ease with which President Trump was able to dump the JCPOA, and the inability of outraged Europeans to contest his imposition of unilateral sanctions, created a healthy skepticism in Iran about the deal’s value. Tehran has realized that an executive agreement like the JCPOA has no legal force in the U.S. It is not simply that a future president could follow Mr. Trump’s footsteps and reject the nuclear deal. President Biden could sign the JCPOA one week and reimpose American sanctions on whatever grounds he chose the next, and Iran would have no recourse.

Given that the nuclear deal or anything like it has zero chance of attracting the two-thirds majority of senators necessary for treaty ratification, the most Tehran can get out of the negotiating process is a Biden pinky-swear. For hard-nosed Iranian mullahs and Revolutionary Guards raised on tales of U.S. perfidy, the idea of trusting the Great Satan’s word—after he’s already fooled you once—is laughable. They see no real reason to pay any kind of price for such a weak agreement.

On the American side, too, the deal is looking less attractive within and without the administration. In retaliation for Mr. Trump’s withdrawal from the JCPOA and the additional sanctions he imposed, Iran accelerated its uranium enrichment and other bomb-related activities to the point where the 2015 nuclear deal begins to look meaningless. Sunset provisions built into the original agreement have already begun to kick in, and key restraints on both bomb-making and missile-development programs begin to disappear this presidential term.

This all puts the administration in a tricky spot. The JCPOA remains a sacred cause for many Democrats, and some believe that without re-entering the Iran deal the U.S. will be forced into an impossible choice between accepting an Iranian bomb or launching yet another Middle East war. But as Tehran delays negotiations while launching one provocation after another across the region, it’s making Mr. Biden’s path back to the JCPOA as awkward and humiliating as it possibly can.

Rather than seeing American withdrawals from Afghanistan and Iraq as friendly gestures meriting a constructive response, the mullahs appear to have interpreted them as a sign that the Biden administration can be safely defied. Likely believing the White House is bent on Middle East withdrawal, no matter the cost, Tehran seems to have decided to double down on its confrontational approach to capitalize on perceived U.S. weakness.

In the process, Iran is destabilizing the region and increasing the danger of war. In recent weeks, Iranian-backed militias have fired rockets into American bases in Syria and Iraq, and Hezbollah has launched rocket attacks on Israel from southern Lebanon. Attacks by drones and hijackers endanger shipping in the Gulf. Israel and its newfound Arab allies face an existential choice. Will they accept Tehran as a regional hegemon as the U.S. withdraws, or will they resist? If they choose the path of defiance will America be able to stay out of the ensuing war?

A deepening confrontation with a radicalizing Iran is not what the Biden administration expected from its Middle East policy, but that is the reality with which it must cope. Attempting to placate Tehran through patience and restraint will likely only stoke the regime’s ambitions. The smell of blood in the water rarely inspires feelings of moderation and restraint among sharks.

Journal Editorial Report: Paul Gigot interviews Clifford May of the Foundation for Defense of Democracies. Image: Jalil Rezayee/Shutterstock The Wall Street Journal Interactive Edition