Turkey is rapidly catching the Syrian disease, threatening to become another Middle Eastern country torn apart by internal factions with a reputation as a playground for contending international forces. But as an important member of the NATO alliance, Turkey plays a much more important role in relations among the European Union, the United States and Vladimir Putin’s increasingly aggressive Russia.

The analogies to Syria grow stronger as the outcome is ever denser in murk and uncertainty. Trouble arrived and prospered with the arrival of President Recep Tayyip Erdogan. With the decline of his once-spectacular popularity, Mr. Erdogan has developed a bad case of unrequited egomania.

As the successful mayor of Istanbul, Mr. Erdogan came to the presidency offering hope and change, but eventually disdained government of the people, by the people, for the people. “Democracy is like a streetcar,” he once said. “When you come to your stop, you get off.” His stop seems to be at an authoritarian state of his making. But his streetcar lost its trolley wire and jumped the tracks with the loss of his parliamentary majority four months ago.

Like Bashar Assad in Syria, Mr. Erdogan refuses to make compromises with his considerable opposition. The economic boom is fading. He has all but abandoned an attempt to join the European Union after his potential Western partners spoke of doubts about whether Turkey could meet the requirements of free governments.

Mr. Erdogan’s chief foreign policy, to build a coalition of friends to surround Turkey, has accomplished the exact reverse: He is arguing and feuding with all his neighbors and the major powers, including the United States. This is the man President Obama once called one of a handful of leaders with whom he was on intimate terms.

Evidence of the rift with the United States surfaced with the announcement that the United States, along with Germany, will withdraw the Patriot missiles which Mr. Erdogan asked for when his relations with Mr. Assad soured. The Pentagon’s official explanation is that the missiles require modification. But there’s diplomatic speculation that it’s because Mr. Obama doesn’t want to have anything to do with Turkey’s difficulties on its Syrian border, despite NATO assurances of support.

The question for the West is whether Mr. Erdogan will make a radical turn now toward reconciliation. The alternative looks like chaos. A bomb explosion last week in Ankara demonstrates the risks ahead for an uncertain ally.