Turkish President Recep Tayyip Erdogan delivers a speech in Ankara this week. (Adem Altan/Agence France-Presse via Getty Images)

RUSSIAN AIRSTRIKES are not the only complicating factor as the Obama administration continues to search for a Syria strategy. Turkish President Recep Tayyip Erdogan appeared ready to join with the United States in a more determined campaign against the Islamic State in July, when he agreed to allow U.S. planes to conduct missions from a Turkish air base. Now that is looking like a feint. In the days after the agreement, the Turkish military launched an all-out assault not on the Islamists but on Kurdish insurgents in Turkey and Iraq, breaking a two-year cease-fire. Rather than help U.S. operations, the campaign is complicating U.S. efforts to support a Kurdish militia inside Syria that has emerged as the strongest anti-Islamic State ground force.

Mr. Erdogan’s objective, it turns out, was not to turn the tide of war in Syria but to reverse his failure to consolidate his power in Turkey. In June the would-be strongman was the big loser of a parliamentary election that he hoped would give his Justice and Development (AK) Party a majority sufficient to rewrite the constitution and grant him Putinesque powers. The ruling party not only failed to meet that threshold but also lost its majority, thanks in large part to the rise of a leftist Kurdish party. The Peoples’ Democratic Party (HDP) won the support not just of the country’s large Kurdish minority but also of secularists and liberals who wished to thwart Mr. Erdogan’s ambitions.

After launching his military campaign against the insurgents of the Kurdistan Workers’ Party (PKK), Mr. Erdogan used his position as president to obstruct the formation of a new government and called new elections for Nov. 1. His aim is to push the Kurdish party below the 10 percent of the vote it needs to enter parliament while attracting votes from Turks who previously supported right-wing nationalist parties. That, he hopes, will give him the supermajority he seeks — or, at least, a new AK government that will treat him as a de facto strongman even without constitutional changes.

So far, polls suggest that the president’s gambit may fail. But he is succeeding in destabilizing Turkey. Much of the southeast of the country has been designated as military zones, and hundreds on both sides have been killed. Responding to inflammatory speeches by Mr. Erdogan, pro-government mobs have attacked nearly 200 buildings belonging to the HDP, along with the Istanbul offices of one of the country’s leading newspapers. Three foreign journalists have been deported from Turkey, and a prosecutor is threatening to strip the HDP leader of his political immunity on incitement charges. For his part, the Kurdish leader, Selahattin Demirtas, has warned that the country is on the verge of civil war.

Considering the potential to disrupt the war against the Islamic State, the Obama administration has reacted mildly to Mr. Erdogan’s campaign. A State Department spokesman has been critical of the attacks on the media, saying “the quality of Turkey’s democracy matters to us.” He also said the administration is talking to the Turkish government about U.S. support for the Kurdish forces in Syria. Given the slim chances that Mr. Erdogan will respond reasonably, Washington can only hope that Turkish voters rebuff him again.