The weakest point in President Obama’s defense of his deal with Iran is his claim that “it is a good deal even if Iran doesn’t change at all.”

Let’s consider that scenario. An Iran that does not change will reap hundreds of billions of dollars in fresh revenue from the lifting of sanctions, and it will surely use much of that to fund its ongoing military adventures in Iraq, Syria, Lebanon and Yemen. It will supply more weapons to Hamas and other radical Palestinian groups, and invest more in its long-range missiles, cyberweapons and other military technologies not covered by the agreement. It will continue developing advanced centrifuges for uranium enrichment and after a decade will begin installing them.

By Obama’s own account, in 13 or 14 years Iran will reemerge as a threshold nuclear state with a breakout time “almost down to zero.” It will still seek domination of the Middle East and the elimination of Israel, but with far greater resources and the capability to build a nuclear weapon at any time of its choosing. A future president, administration officials concede, will have to go back to the same strategy — sanctions, sabotage and the threat of force — that Obama now proposes to set aside, but the odds of preventing a nuclear Iran will be considerably worse than they are now.

To say the least, that future president is unlikely to agree that Obama made a good deal.

So let’s be honest: Everything depends on Obama’s hope that nuclear detente will change Iran. “If in fact they’re engaged in international business, and there are foreign investors, and their economy becomes more integrated with the world economy, then in many ways it makes it harder for them to engage in behaviors that are contrary to international norms,” is the way he put it to National Public Radio.

Such an Iran would be less likely to try to cheat on its nuclear commitments or to rapidly expand its uranium enrichment when restrictions expire. As Obama sees it, rather than seek to destroy Israel or Sunni Arab regimes such as Saudi Arabia, it would settle for a regional “equilibrium” that would, in turn, open the way to compromise solutions to the wars in Syria and elsewhere. It would have “a different kind of relationship” with the United States.

Obama may deny that this transformation is baked into the terms he agreed to. But it’s well known that his belief that “engagement” with rogue regimes leads to peaceful and positive change is the distinguishing foreign policy idea of his presidency, one that he has applied to Burma and Cuba, as well as to Iran. It explains why he would agree to temporarily restrain, rather than eliminate, Iran’s capacity to build a bomb. There’s no point in simply buying time unless you expect something to change.

The biggest question about the accord is consequently not how quickly sanctions are lifted or whether inspections are rigorous enough. It is whether “those forces inside of Iran that say, ‘We don’t need to view ourselves entirely through the lens of our war machine’ . . . get stronger,” as Obama told the New York Times.

So can they? Fifteen years ago, most Western experts on Iran might have said yes. That was when the reformist president Mohammad Khatami, elected in a 1997 landslide, was encouraging a “dialogue of civilizations” and saying it was up to the Palestinians to decide the future of their homeland; when liberal students marched at universities and a robust independent press demanded even greater freedoms. In 2009, when the “Green Movement” surged into the streets following a disputed election, the possibility of radical political change in Tehran once again seemed real.

It turned out, however, that both Iranian liberals and Western analysts underestimated the strength of Iran’s deep state — the Revolutionary Guards, the reactionary clergy, the hard-line judiciary. Those forces crushed both Khatami and the Green Movement; presiding over them is Supreme Leader Ayatollah Ali Khamenei, who last week reiterated his abiding hatred for the West and everything it represents.

Today it’s difficult to find an expert who believes Iran will soon evolve into a more benign power, notwithstanding the 2013 election of the moderate Hassan Rouhani as president. Present and former senior administration officials I consulted said they expected the Iranian regime would remain the same in the next few years, or maybe get worse. One predicted Khamenei — if he doesn’t kill the accord outright — would set out to prove that it won’t change the state’s “revolutionary” agenda.

That widely shared analysis may well be too gloomy. But it probably explains why Obama keeps insisting in media interviews that he’s not banking on an Iranian transformation. In reality, he is. It’s the apotheosis of his worldview, the sine qua non of the nuclear deal — and the riskiest bet of his presidency.

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