The first person to suggest that Donald Trump would have a conflict of interest in dealing with Turkey and Turkish President Recep Tayyip Erdogan was Trump himself.

“I have a little conflict of interest because I have a major, major building in Istanbul and it’s a tremendously successful job,” Trump told Stephen K. Bannon (who was then working for Breitbart) in December 2015. “It’s called Trump Towers — two towers instead of one, not the usual one, it’s two."

“I’ve gotten to know Turkey very well and they are amazing people, they’re incredible people,” Trump continued. “They have a strong leader” — Erdogan — “the strong leader is now fighting pretty much with Putin, if you look at what’s going on, there’s a lot of, there’s a lot of angst and a lot of anguish going on over there.”

Later, Bannon asked directly about how Trump would assuage concerns about a conflict of interest.

“Hey, look, this guy’s got vested business ventures all over the world,” Bannon asked in the voice of a swing voter. “How do I know he’s going to stand up to Turkey?”

The easy answer, the answer that might have been offered by any prior president, was that Trump would divest of his investments in Turkey before taking office. Instead, Trump offered another murky response, including an assertion that “we should have been able to win easily but we haven’t used the right military thought process.”

Nor did he divest, of course. Trump Towers Istanbul is still part of the Trump Organization and still generates revenue for Trump himself.

When the Trump Organization launched the project in 2012, both Donald Trump and his daughter Ivanka traveled to the country. Trump tweeted celebrations of the project several times while there. Ivanka, now a senior official in Trump’s White House, praised Erdogan directly.

The Trump administration’s unusual relationship with Erdogan has been an undercurrent from its outset. Trump’s first national security adviser, Michael Flynn, was working for the Turkish government during the 2016 campaign, even writing a column defending Turkey for the Hill that ran on the day Trump was elected. When Erdogan pushed for a referendum advocating changes to Turkey’s Constitution that helped him consolidate power after a 2016 coup attempt, the State Department criticized both the effort and the suspect vote totals. Trump offered his congratulations.

Erdogan visited Trump in May 2017 before visiting the residence of Turkey’s ambassador to the United States in Washington. While Erdogan was at the house, Erdogan’s bodyguards attacked protesters standing across the street — an attack that may have been ordered by Erdogan himself. Then-press secretary Sean Spicer had no comment about the brawl. Trump referred to Erdogan as “a friend of mine” even after that incident.

This friendship has no better manifestation than Trump’s decision late Sunday to give Turkey free rein in northern Syria at the likely expense of the United States’ Kurdish allies in the region. Turkey has long struggled against nationalist Kurdish forces in the region, given the country’s overlap with the traditional Kurdish homeland. That struggle is often military, and Trump’s decision to cede security efforts in the region to Turkey is expected to allow Turkey to further engage Kurdish forces directly.

It is a decision that spurred objection from unexpected critics. Trump’s former envoy in the fight against the Islamic State blasted the move, as did fervent Trump ally Sen. Lindsey O. Graham (R-S.C.). Graham called it a “disaster in the making” and said the move was “shortsighted and irresponsible.” Graham appears to have not been briefed on the decision before its being announced by the White House. The Pentagon defended its existing approach to northern Syria and Turkey on Saturday, suggesting that the Defense Department and Secretary Mark T. Esper — about a month into the job — were not the drivers of a decision announced after Trump and Erdogan spoke on the phone. (In August, as The Post’s Dan Lamothe reported, Esper called a Turkish move against the Kurds “unacceptable” and said that the United States didn’t have “any ambition to abandon” our Kurdish allies.)

So why make this move?

Trump is defending it on Twitter as having been a realization of his campaign-trail objections to prolonged military conflicts, an argument that relies in part on misrepresenting the original scope of U.S. involvement in the region. He’s threatened to destroy Turkey’s economy should the country take an action that in Trump’s “great and unmatched wisdom” is “off limits.”

He’s in essence applying the same defense that he offered to Bannon, that he’s simply using “the right military thought process.”

Bannon’s question, though, also lingers. How can the public be fully confident that Trump is separating his business-based relationship with Erdogan from his presidential one? There are other unsavory possibilities driving the decision, including Trump’s demonstrated affection for the anti-democratic strongman. That, too, derives from Trump’s unusual approach to the presidency: Past presidents would have given Erdogan a colder shoulder given the Turkish leader’s approach to politics in his country, easily avoiding any appearance that they gave Erdogan space out of sympathy to his approach to leadership.

Questions exist about this decision for the obvious reason that it reverses U.S. pledges to our allies in the region. But they exist, too, because Trump has repeatedly made other decisions centered on Turkey that would lead any reasonable observer to wonder what’s going on. Beginning with that question raised by Bannon nearly four years ago.

Trump’s Monday morning insistence that he’d be keeping an eye on Turkey’s actions didn’t include objecting to engaging the United States’ Kurdish allies.