In recent years, U.S. officials have complained that Turkey allowed jihadis to slip across its southern border to join ISIS, an Al Qaeda faction, and other militant groups in Syria. Turkey then invaded Syria, this fall, to fight the U.S.-backed Kurdish militia that defeated ISIS. Turkey has also cozied up to Russia militarily. It has coöperated with Iran, and a state-owned bank facilitated a multibillion-dollar Iranian scheme to evade U.S. sanctions. At home, Erdoğan has cracked down on political opponents, the media, business leaders, academics, and even his own military to consolidate his rule. Thousands have been arrested in violation of the human-rights principles of the European Union, which Turkey long sought to join.

“It is fair to ask if Turkey is still really an ally of the United States in anything more than name,” Phil Gordon, a senior fellow at the Council on Foreign Relations who served as the Obama Administration’s White House coördinator on Middle East policy, told me. “Ten years ago, we saw Turkey as a country moving toward the United States and the West, reforming and growing economically, democratizing and getting the military out of politics, seeking to join the European Union, and working with the United States in NATO from Afghanistan to the Balkans.” But in the past few years, he said, Turkey has moved in the opposite direction. “Turkey remains an important potential partner of the United States, but the days when the United States aspired to a ‘model partnership’ based on common values and interests are over.”

The crisis is the worst in the modern history of relations between Washington and Ankara, Gönül Tol, the director of Turkish studies at the Middle East Institute, in Washington, told me. “Anti-Americanism has always been there, but it has peaked in the last few years,” she said. “An overwhelming majority of people in Turkey think that Russia is a better ally, and that the bigger national-security threat comes from the U.S.”