Turkey's main pro-Kurdish party and its leftist allies called on voters Friday to back President Recep Tayyip Erdogan's main rival in the May 14 polls.
The announcement pushes one of Turkey's largest voting blocs behind opposition candidate Kemal Kilicdaroglu and further complicates Erdogan's path to a third decade of rule.
The Peoples' Democratic Party (HDP) -- the third-largest in Turkey's parliament -- decided last month not to field a presidential candidate.
It then strongly hinted that it would back Kilicdaroglu without officially endorsing his candidacy.
But both the party's co-leader and its leftist electoral alliance issued statements Friday calling on voters to rally around the most likely candidate to beat Erdogan.
"In this historic election, we call on the people of Turkey to vote for the Labour and Freedom Alliance in the parliamentary elections and for Kemal Kilicdaroglu in the presidential elections," the HDP and its allies said in a statement.
The HDP won more than 10 percent of the vote in past national elections and represents a community accounting for about a fifth of Turkey's population.
Kurds suffered repressions under successive secular governments and helped Erdogan and his Islamic-rooted party seize power two decades ago.
Erdogan lifted linguistic and cultural restrictions on the community and tried to end a bloody Kurdish struggle for an independent state in Turkey's southeast through talks.
But a breakdown of those negotiations in 2015 was followed by a new wave of violence and a government clampdown on Kurdish groups.
Erdogan's government jailed thousands of activists and replaced dozens of elected Kurdish mayors with state trustees.