Washington ? Turkey’s political tensions were sharply evident Thursday, as the country’s leading Kurdish politician accused President Recep Tayyip Erdogan of “supporting ISIS” in the past. He claimed Erdogan wants early elections as part of a strategy of “attacking the Kurdish movement” and reversing its recent political gains.

Selahattin Demirtas, the leader of the Peoples’ Democratic Party, or HDP, made the charges in an hourlong telephone interview from Diyarbakir, in southeastern Turkey. He lived up to his reputation as an outspoken opponent of Erdogan and champion of Kurdish rights. His comments framed some of the big issues in the parliamentary campaign that is likely this fall.

Demirtas claimed that Erdogan had agreed last month to allow U.S. warplanes to operate from Incirlik air base against the Islamic State, or ISIS, “to recover the reputation he lost” because of his earlier inactivity against the extremists. “He’s trying to get away from the pro-ISIS burden on his shoulders, because they’ve been supporting ISIS for some time,” he contended.

Asked for evidence to support such a serious charge, Demirtas responded through a translator: “Turkey let ISIS use its territory for many purposes. (Erdogan) did not effectively close the border to prevent ISIS militants from crossing. We see that Turkey was not an effective partner in the anti-ISIS coalition established by the U.S.” 

Later in the interview, I asked Demirtas about his reported claim that a bloody suicide bombing July 20 at Suruc in southeastern Turkey was linked to a secret “Gladio” organization (a cover name for NATO intelligence activities during the Cold War). He said the Turkish president “knows everything that is happening in this country,” and that “Turkish security forces did not somehow take any precaution or prevent such bombings.”

Erdogan has dismissed the Suruc allegation. “This is a statement that does not have any rhyme or reason and is vulgar,” he said, according to the Turkish newspaper Hurriyet.

Demirtas’ clash with Erdogan will intensify if new parliamentary elections are called. That seems likely after the breakdown Thursday of coalition talks between Erdogan’s Justice and Development Party, or AKP, and a centrist rival known as the CHP. Although the AKP won the largest number of seats in the most recent elections just two months ago, it was blocked from forming a government outright by the surprising success of Demirtas’ HDP, which won 13 percent of the vote.

I asked Demirtas about the Obama administration’s deal with Erdogan to use Incirlik for U.S. and Turkish strikes against Islamic State targets in Syria. Many commentators have charged that under cover of the anti-extremist coalition, Erdogan’s main bombing targets have been bases of the banned Kurdistan Workers’ Party, or PKK, which is allied with a Syrian Kurdish militia that has been America’s most effective ally against the Islamic State in Syria. Demirtas declined to criticize the U.S. role.

“I don’t believe that the U.S. betrayed the Kurds” in the Incirlik deal,” he said, adding: “I would support any measure that would be taken against ISIS.”

Demirtas said the Obama administration could help ease the toxic political situation in Turkey by encouraging peace talks between Erdogan’s government and the PKK, which the U.S. officially lists as a terrorist group. Demirtas repeated his past criticism of attacks by the PKK and said the group’s imprisoned leader, Abdullah Ocalan, “is ready to resume all the existing peace talks” that were broken off earlier this year. He urged the U.S. to “create incentives” for resuming the peace process.

Many analysts argue that the Kurdish moment has arrived in the Middle East. Kurdish fighters, operating with close U.S. air support in Iraq and Syria, have had some of the few big victories over the past year against the Islamic State. Demirtas has emerged in Turkey as a fearless advocate of democracy and reform.

Like most pragmatic Kurdish leaders, Demirtas recognizes that for the foreseeable future, Kurdish ambitions must accommodate existing nation-state boundaries. But he’s right that the secular, sophisticated Kurdish people “should not be sacrificed to short-term tactical moves.”

— David Ignatius is a columnist for Washington Post Writers Group.