French President Emmanuel Macron complained during the NATO summit in London earlier this month about Turkey's decision to buy a Russian missile-defense system and its invasion of Syria, musing about how Turkey could justify its continued membership in the alliance if it counties to flout its interests at every turn.

These comments, only the latest round of complaints about Turkey's behavior toward its Western NATO allies, inspired speculation about whether NATO could formally expel Turkey. But aside from whatever legal complications might lie in wait, we posit that there's another more fundamental reason why NATO likely won't be able to expel Turkey. Because Turkish President Recep Tayyip Erdogan would likely quit first.

That's right: Although Trump and Erdogan have tried to maintain at least the veneer of a personally amicable relationship, and though Trump has at times defied his own senior NatSec officials to offer a major sop to Erdogan (like when Trump pulled US troops out and stepped aside to allow the Turkish invasion, the the horror of Europe), Erdogan's increasingly tight relationship with Russia - a relationship built on defense and energy ties - is becoming impossible for many western leaders to countenance.

Congressional hawks like Lindsey Graham (for the Republicans) and Chris Van Hollen (on the Democratic side) have already successfully pushed Trump to "announce" more sanctions against Turkey via Twitter. And they might be able to finally push him to follow through, too.

In response to this and myriad other slights both perceived and real, Erdogan made it clear on Monday that he's had about enough of this harassment from his supposed "allies" in the West. Because when it comes to Trump cards, Erdogan still has one to play.

According to Bloomberg, Erdogan warned that he could shutter two of the most important NATO bases in the world if more sanctions are imposed.

In the minds of US NatSec officials, Erdogan's threat is an extremely low blow. An early-warning radar at Turkey's Kurecik air base is a critical component of NATO's early-warning defense system against ballistic missile attacks. And the Incirlik air base in southern Turkey is critical to tactical air strikes and drone attacks throughout the region.

"If it is necessary to shut it down, we would shut down Incirlik," Erdogan told AHaber television on Sunday. "If it is necessary to shut it down, we would shut down Kurecik, too." [...] "If they put measures such as sanctions in force, then we would respond based on reciprocity," Erdogan said. "It is very important for both sides that the U.S. should not take irreparable steps in our relations."

Additionally, Erdogan warned the US not to recognize the Turkish genocide of Armenians in the early part of the 20th century, an issue that has long been important for Erdogan.

Until now, the US and NATO military presence in Turkey has been held sacred, even as the relationship between the two countries became increasingly bitter over the past two years. Those aren't the only two bases in Turkey: the US has for decades heavily leaned on Turkey as critical to its policing of the Middle East.

Bottom line: It's Turkey's party, and it can buy missiles from Russia if it wants to. After all, placating Russia is important for an energy importer like Turkey. Russian energy subsidies can be a huge economic boon for an economy - just look at Belarus.

Plus, now that Erdogan has cemented his control over the levers of power in Turkey, even if his decision to re-run the mayoral elections in Istanbul didn't turn out quite as well as he had probably hoped. He's eager to establish Turkey as a regional power, and bending to the US on this would make him look week.

Of course, for the US, Erdogan's demands present a difficult dilemma: The US and NATO need Turkey to host its bases, but they're worried that, if the S-400 system becomes fully operational (expected in April), many worry the Russian system could be used to collect intelligence on the stealth capabilities of the F-5 fighter jet.

Now, will President Trump risk calling Erdogan's bluff? That remains to be seen.