As he moves on to his fourth national security adviser in less than three years, it has become clear that President Trump’s foreign policy is in shambles. It has produced turmoil but achieved almost nothing. Despite all the boasts, there are no new deals with China, Iran, North Korea, or the Taliban or between the Israelis and Palestinians — just uncertainty, disappointment and lots of bruised feelings.

Trump informed the world that he was a great dealmaker. Yet other than minor changes to the North American Free Trade Agreement and the U.S.-South Korea trade pact — changes that Robert Zoellick, U.S. trade representative under President George W. Bush, believes have probably made things worse — Trump has achieved little. There are many reasons for this. The Trump administration has been chaotic and undisciplined, bringing the ethos of a mom-and-pop real estate shop to one of the largest and most complex institutions in the world, the U.S. federal government. Trump has had more turnover in senior staff in 2½ years than most administrations have in a full term.

The central problem, however, is that Trump — despite his boasts — is a bad negotiator. With both Kim Jong Un and the Taliban, he gave away crucial leverage right from the start. The North Koreans have wanted one-on-one meetings with the U.S. president for decades and were always told this would happen only after they made concessions. Trump gave away that prize immediately, hoping to charm Kim into giving up his nuclear weapons. So far, Kim 1, Trump 0.

With Afghanistan, Trump excoriated President Barack Obama for announcing deadlines for troop withdrawals, making the sensible point that it allows the enemy to wait you out. And yet, Trump has done something similar, repeatedly announcing his eagerness to quit — and then being surprised that the Taliban sought to press its advantage. Consider Trump’s muddle on Afghanistan: He fired national security adviser John Bolton, apparently, because Bolton objected to making a deal with the Taliban — except that Trump canceled talks with the Taliban, effectively agreeing with Bolton.

With Bolton gone, Trump does have the opportunity to act on his instincts and actually get something done — a new Iran nuclear deal. His reimposition of sanctions on Iran has been surprisingly, brutally effective. Because of the dollar’s pivotal role in the international economic system, and despite the fact that other countries want to do business with Iran, they simply can’t conduct major transactions without using the dollar and, thus, the U.S. financial system.

Iran is a proud, ancient civilization and a canny regional power. It will not simply surrender. But it might agree to a new deal, one that achieves more than the Obama accord. Were that to happen, Trump could reasonably argue that while he took an unconventional approach, he was able to get what no one thought possible — a new, improved Iran deal.

For this to work, Trump will have to overrule some of his most hawkish advisers and find a path to a real negotiation. The Iranians will likely sit down only if sanctions are suspended during the negotiations. They will want to describe any changes that are made as additional measures to implement the 2015 deal, rather than a new deal. Whatever; that’s what diplomats are for.

Trump’s goal should be to get the Iranians to extend the time horizon of key parts of the deal by approximately five years. He will not be able to make much headway on Iran’s ballistic missile arsenal — Tehran views that as its defense against the vast Saudi military. (It has bitter memories of being defenseless against hails of rockets and missiles by Saddam Hussein during the Iran-Iraq War.) On Iran’s other regional activities — its support for Hezbollah, for example — it might well be willing to talk, but Trump will have to consider whether this would expand the negotiations into an interminable conversation involving Israel and the broader Middle East. In addition, were Iran to agree to some restraint in these areas, the United States would have to reciprocate by making some concessions of its own — say, the relaxation of other U.S. sanctions against Iran. I doubt Trump or Congress would be willing to do that.

Most important, to get an Iran deal, Trump would have to work against his fundamental urge always to claim victory. Maybe this works in business, where there are single transactions — though it might explain why so few people ever do business with Trump again. But foreign policy is about long-term relationships, not about solo transactions. Both sides have their own domestic politics and constituencies. Each needs to be able to say it has achieved success. If Trump can stomach that, he could emerge with something rare in his tenure so far, an actual foreign policy win.

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Read more:

Daniel W. Drezner: Worst. Negotiator. Ever.

Henry Olsen: Trump’s decision to cancel peace talks with the Taliban could be a huge blunder

Max Boot: John Bolton was bad. His departure might be worse.

Erik Wemple: Tucker Carlson: John Bolton is a ‘man of the left.’ Or a ‘neocon.’ You decide.

The Post’s View: John Bolton’s legacy: Chaos, dysfunction and no meaningful accomplishments