In an interview in late 2006, I asked then-Senator Barack Obama to talk about the challenges to rational deterrence theory posed by the behavior of rogue states. “Whatever you want to say about the Soviets,” Obama answered, “they were essentially conservative. The North Korean regime and the Iranians are driven more by ideology and fantasy.”

Earlier this year, I asked Obama the following question: “What is more dangerous: Sunni extremism or Shia extremism?”

His answer was revealing, suggestive of an important change in the way he has come to view the Iranian regime. He started by saying, as would be expected, “I’m not big on extremism generally.” And then he argued—in part by omission—that he finds the principal proponent of Shiite extremism, the regime in Tehran, more rational, and more malleable, than the main promoters of Sunni radicalism.

“I don’t think you’ll get me to choose on those two issues,” he said. “What I’ll say is that if you look at Iranian behavior, they are strategic, and they’re not impulsive. They have a worldview, and they see their interests, and they respond to costs and benefits. And that isn’t to say that they aren’t a theocracy that embraces all kinds of ideas that I find abhorrent, but they’re not North Korea. They are a large, powerful country that sees itself as an important player on the world stage, and I do not think has a suicide wish, and can respond to incentives. And that’s the reason why they came to the table on sanctions.”

Since becoming president, Obama has made the argument that Iran could be induced, cajoled, and pressured into compromise, a view that has been proven provisionally, partially, correct: Sanctions, plus Obama's repeated (and, to my mind, at least, credible) threat of military action, convinced Iran to temporarily halt many aspects of its nuclear program in exchange for limited sanctions relief. But Obama and his international partners have been less successful at bringing Iran to permanent denuclearization.

A long-term, verifiable arrangement that keeps Iran perpetually a year or more from nuclear breakout is surpassingly important for the national security of the United States (as Obama noted in this interview); for the health and safety of America’s friends in the Middle East; and for the cause of nuclear nonproliferation in the world’s most volatile and dangerous region. Over the past year, the two sides of international nuclear negotiations have apparently moved somewhat closer to each other, and when the second round of talks came to an end without achieving a deal, both sides agreed that yet another negotiation extension was in order. As Iran and its interlocutors move into what stands to be the fateful year for these negotiations, a credible deal does not look to be achievable; so far, at least, the Iranians seem unwilling to make the truly creative concessions necessary to meet the West's minimum requirements.

Especially if a deal is ultimately proven to be unachievable, another question will arise: Is the price the U.S. has paid to reach this elusive deal too high? An admirable aspect of Obama’s foreign-policy making is his ability to coolly focus on core issues to the exclusion of what he considers to be extraneous matters. This is also, however, a non-admirable aspect of his policymaking, in particular when the subject at hand is Iran’s role in supporting the killer Assad regime in Syria.

Obama seems to believe that a nuclear deal is, in a way, like Casaubon's key to all mythologies: Many good things, he believes, could flow from a nuclear compromise. In an interview last week with NPR’s Steve Inskeep, the president suggested that a nuclear agreement would help Iran become “a very successful regional power that was also abiding by international norms and international rules.” This, he said, “would be good for everybody. That would be good for the United States, that would be good for the region, and most of all, it would be good for the Iranian people.”

This is a wonderful notion, the idea that the end of Iran’s isolation could lead it to moderate its more extreme impulses. But there isn’t much in the way of proof to suggest that Iran’s rulers are looking to join an international order whose norms are defined by the United States and its allies. In fact, there is proof of something quite opposite: Iran seems as interested as ever in becoming a regional hegemon, on its own terms. And its supreme leader, and his closest confidants, have made it clear, over and over again, that he is not interested in normalizing relations with the United States.

Across the greater Middle East, Iran's efforts to extend its influence have been blunt and brutal: It supports Shiite insurrections in Yemen and Bahrain; it attempts to manipulate Lebanese politics through its Beirut-based proxy, Hezbollah; it intervenes in Gaza and against the already-fading hope for a two-state solution to the Israeli-Arab crisis; and certainly its unceasing threats to eradicate a fellow member-state of the United Nations, Israel, suggest that Iran’s supreme leader, Ayatollah Ali Khamenei, has a vision for Iran that differs from Obama’s.

But nothing underscores the Iranian regime’s imperialistic, hegemonic nature more than its support for the Assad regime in Damascus. Without Iran’s assistance, Assad would have fallen a long time ago. The death toll in Syria is more than 200,000; half of Syria's population has been displaced. These dark achievements of the Assad regime would not have been possible without Iran. Thousands of Hezbollah and Iranian Revolutionary Guard Corps troops and advisers, plus Iranian weaponry, have made all the difference for Assad. As a recent study by the Middle East Institute states:

It is no longer accurate to describe the war in Syria as a conflict between Syrian rebels on the one hand and Bashar al-Assad's regime forces “supported” by the Iranian Revolutionary Guards (IRG), Hezbollah, and Iraqi militias on the other. Most major battles in Syria—along the frontlines of regime-held areas—are now being directed and fought by the IRG and Hezbollah, along with other non-Syrian Shi‘i militias, with Assad forces in a supportive or secondary role. ...

One result of this heavy Iranian involvement in the war in Syria has been a change in the nature of the relationship between the Syrian and the Iranian regimes. From historically being mutually beneficial allies, the Iranian regime is now effectively the dominant force in regime-held areas of Syria, and can thus be legally considered an “occupying force,” with the responsibilities that accompany such a role.

There was no commensurate effort made by opponents of Assad to help those Syrians who were trying to overthrow him. President Obama called on Assad to go, but kept the U.S. on the sidelines through the first years of the Syrian civil war, for reasons he has explained in many places, including here.

Today, the U.S. and its allies are fighting in the Syrian theater, but they are fighting Assad’s putative enemies, the Sunni extremists of ISIS, not Assad and his Iranian allies. And yet ISIS is a derivative problem of a larger crisis: Without Assad—which is to say, without Iran—there would be no ISIS “caliphate” in Syria in the first place. The midwives of ISIS are Assad, Hezbollah chief Hassan Nasrallah, and Ayatollah Khamenei.

If Assad had been overthrown early in the civil war, a more moderate, multi-confessional Syrian government could have plausibly emerged to take its place. The early rebels, who frightened the Assad regime to its core, were not seeking to build a cross-border caliphate on a foundation of medieval cruelty; they were simply seeking to remove Assad’s boot from their necks. As the Assad regime, with Iran’s invaluable help, recovered from the first blows of the rebellion, many Sunni Syrians, seeking help everywhere but finding it mainly among radicals, became radicalized themselves. This was an explicable, if not justifiable, reaction to the mortal threat posed by what they saw as a massed Shiite threat.

Earlier this year, in a conversation about the Obama administration’s Middle East strategy, Senator John McCain brought me up short when he criticized the president for launching attacks on a symptom of the Syrian civil war, ISIS, rather than its root cause. He told me that the U.S. should be battling the Assad regime at the same time it attacks Sunni terrorists. I asked him the following question: “Wouldn’t the generals say to you, ‘You want me to fight ISIS, and you want me to fight the guys who are fighting ISIS, at the same time? Why would we bomb guys who are bombing ISIS? That would turn this into a crazy standoff.’”

McCain answered: “Our ultimate job is not only to defeat ISIS but to give the Syrian people the opportunity to prevail as well. ... If we do this right, if we do the right kind of training and equipping of the Free Syrian Army, plus air strikes, plus taking out Bashar Assad’s air assets, we could reverse the battlefield equation.”

There is even less reason to believe today that the Free Syrian Army, such as it is, is capable of fighting the Assad regime (and ISIS) effectively. So at this late stage, McCain’s policy prescriptions may be unrealistic. But his diagnosis of the core problem seems tragically accurate.

“I don’t think ISIS would exist if Bashar al-Assad had been removed two or three years ago,” McCain told me when we revisited the question earlier this month. “He was on his way out until the Iranians brought in 5,000 Hezbollah fighters, and the Iranian Revolutionary Guard Corps came in, to train Assad’s troops and provide them with weapons, including the barrel bombs, which are horrible weapons of war.”

McCain argues that the Obama administration has avoided confronting Assad in part for fear that doing so would alienate Assad’s patrons in Tehran, the same men who are in charge of the nuclear file. “The whole theory hinges on a major breakthrough in the nuclear talks, that once they get their deal, Iran will stop funding Hamas, stop supporting Hezbollah, stop destabilizing Yemen, that they’ll join us in fighting extremism. So they have to get a nuclear deal at all costs, and not do anything in Syria. This is just so farfetched it’s delusional.”

I wouldn’t go so far as to call proponents of this theory delusional, but let's say that they are not approaching the issue of leverage in an effective way. Gary Samore, a former Obama administration official who was in charge of the National Security Council’s Iran nuclear file, told me this month that he would use Iran’s deep exposure in Syria to U.S. advantage.

“Confronting Iran forcefully in Syria and Iraq increases chances for a nuclear deal because Iran will only meet our nuclear demands if it feels weak and vulnerable,” Samore wrote in an email. “Conversely, Iran’s sense that it is winning in Syria and that it is indispensable in Iraq decreases chances for a nuclear because the Supreme Leader won’t make nuclear concessions if he feels strong and ascendant.”

Is it likely that Obama will move toward a policy of containing Iran in Syria, and away from his more accommodationist stance? Arab states that count Iran as an enemy and the U.S. as a friend have asked him repeatedly over the past two years to treat Iran as a root cause of the Syrian catastrophe. But Obama appears focused solely on achieving a nuclear deal with Iran, in part because he seems to believe that Iran is ready to play the part of rational and constructive actor, rather than extremist would-be hegemon. I hope he’s right, and I hope he achieves a strong nuclear deal, but I worry that he is empowering an Iranian government that isn’t about to change in any constructive way. In the meantime, the Iranian regime continues to get away, quite literally, with murder.