“My number-one priority is to dismantle the disastrous deal with Iran,” presidential candidate Donald Trump told the American Israeli Public Affairs Committee last March. “And let me tell you, this deal is catastrophic for America, for Israel, and for the whole Middle East.”

Earlier in the campaign, Trump had been more nuanced about the Obama administration’s diplomatic coup, which in exchange for the lifting of economic sanctions puts Iran’s nuclear weapons program on ice for a decade. In 2015 he told NBC, “It’s very hard to say ‘We’re ripping it up.’” And on MSNBC, also in 2015, he said, “We have a horrible contract, but we have a contract.”

But baited by a rabid and extreme Senator Ted Cruz, Trump’s position hardened, and his promise to the always bellicose AIPAC crowd became a campaign trope. Gradually the trope began to sound like a genuine foreign policy position.

Mike Pence underscored the threat at an October campaign rally in North Carolina: “When Donald Trump becomes president of the United States of America, we’re going to rip up the Iran deal.”

CIA Director Mike Pompeo, who led the opposition to the agreement while he was a member of Congress, was ready to shred the accord. Before he was confirmed, Pompeo tweeted, “I look forward to rolling back this disastrous deal with the world’s largest sponsor of state terrorism.” At his confirmation hearing, he said, “It was my view that the JCPOA was a mistake for American national security.”

White House Chief of Staff Reince Priebus declared the accord is “on life support,” adding that its fate will be decided through a collaborative process, but Trump will have the final word.

At the top of the Trump Team, only Secretary of Defense James Mattis, an implacable critic of Iran while he was an active duty general, seemed to grasp the complexity of the multilateral agreement. Speaking at the Center for Strategic and International Studies last April, Mattis said:

There was the military option; probably could have delayed it for a year or two before we would have to take more military action. Or there was the diplomatic option, where they were aiming to delay it much longer. We’re talking about a decade or more. Without the pause, and despite Iran’s denial and deception, it was clear that Iran could get a weapon.

Yet Trump’s position is clear. As what is formally known as the Joint Comprehensive Plan of Action is neither a ratified treaty nor an executive agreement, he can declare that the United States is no longer a party to it and deliver on his campaign promise.

Campaign posturing notwithstanding, Trump is unlikely to do so. In fact, he has already informally acknowledged the agreement, unsurprisingly in a tweet, in which he put Iran “on notice,” after a missile launch in February:

Iran has been formally PUT ON NOTICE for firing a ballistic missile. Should have been thankful for the terrible deal the U.S. made with them!

— Donald J. Trump (@realDonaldTrump) February 2, 2017

There is little to gain from “dismantling” the “deal,” which the United States, in fact, can’t dismantle, but only abandon. The other parties—Iran, China, France, Russia, the United Kingdom, and Germany—wouldn’t necessarily follow Trump’s lead.

And there is a lot to lose.

Consider.

‘Without the pause, and despite Iran’s denial and deception, it was clear that Iran could get a weapon.’

In 2002, shortly after George W. Bush assigned Iran to the Axis of Evil, Tehran possessed only 200 centrifuges it could use to spin uranium hexafluoride into enriched uranium required to make nuclear weapons. By 2009, that number had grown to 7,000. By 2013, Iran had acquired 20,000 centrifuges, with more than 10,000 spinning and enriching uranium.

There was one missed diplomatic opportunity. In 2003, Iran’s reformist President, Mohammad Khatami (communicating through the Swiss ambassador in Tehran), offered to negotiate his nation’s nuclear program (and a number of other issues) with the United States. The offer came soon after U.S. forces had swept into Baghdad, when the Iraq war looked like a smashing success and Iran’s leaders assumed they were next. Vice President Dick Cheney refused, because “we don’t negotiate with our enemies.”

So there were no negotiations until Secretary of State Hillary Clinton initiated secret talks with Iran in 2013, which led to the agreement signed in Vienna in July 2014.

Today under International Atomic Energy Agency monitoring, Iran is allowed a maximum of 5,060 centrifuges; its four most advanced models are sequestered; its low-enriched uranium stockpile has been reduced by 98 percent, and its heavy water reactor has been disabled and filled with concrete.

And Israel has shelved its plan for a military strike to “take out” Iran’s nuclear facilities.

In a sobering article in the Winter 2017 issue of The Middle East Journal, Israeli scholar Gil Merom described Prime Minister Benjamin Netanyahu’s elaborate plans for a military strike that would destroy, for a few years, Iran’s capacity to create a nuclear weapon. Merom cited former Israeli Prime Minister Ehud Olmert’s description of the $11 billion that Netanyahu had invested in his plan to attack Iran, including building a strategic fleet of more than 100 F-161 and F-151 bombers, developing advanced satellite intelligence and communication capabilities, unmanned aerial vehicles, and enhanced air refueling capabilities.

“In April 2013, when Israeli Defense Force Commander Benny Gantz was asked if Israel could unilaterally attack Iran’s nuclear installations,” Merom writes, “Gantz’s response was: ‘yes, unequivocally.’”

Then Barack Obama, John Kerry, and Wendy Sherman, the chief negotiator for the United States, cheated them out of their casus belli. By 2015, Gantz, and Mossad (Israel’s intelligence service) chief Meir Dagan, and Israeli Air Force director Yuval Diskin “stood firm in opposition to striking,” Merom writes. Because an American-led deal “took the rug out from under the reasoning of a strike, at least for a while.”

Barack Obama’s patient diplomacy also took the rug from under Donald Trump, at least for a while.