ANKARA, Turkey (AP) — President Recep Tayyip Erdogan’s main challenger in Turkey’s presidential race shifted gear and adopted a more nationalist and hard-line stance on Thursday, vowing to send back millions of refugees if he is elected and rejecting any possibility of negotiating for peace with Kurdish militants.

Voters in Turkey will head back to the polls on May 28 for a runoff election after neither Erdogan nor his rival, Kemal Kilicdaroglu, won more than 50% of the votes in Sunday’s first round.

The election will decide whether the country remains under the increasingly authoritarian president for a third decade, or can embark on a more democratic course that the opposition has promised to deliver.

Erdogan had faced electoral headwinds because of the cost-of-living crisis and criticism over the government’s response to a devastating earthquake in February. But with his alliance retaining its hold on the parliament, Erdogan is now in a good position to win in the second round.

Kilicdaroglu, the soft-mannered joint candidate of a six-party opposition alliance, had led a highly positive and uniting campaign, mostly on promises to reverse crackdowns on free speech and other forms of democratic backsliding. He had also campaigned on a pledge to repair an economy battered by high inflation and currency devaluation.

Many of the rallies of his pro-secular main opposition party, Republican People’s Party, or CHP, had ended with Kilicdaroglu making a heart shape with his hands.

This week, however, the 74-year-old politician hardened his rhetoric in an apparent effort to appeal to nationalist voters, including those who voted for a third candidate, nationalist politician Sinan Ogan.

Ogan, who received 5.2% of the votes and is backed by an anti-migrant party, has said he would consider sending migrants back by force if necessary.

“Erdogan! You did not protect the borders or the honor of the country. You brought in more than 10 million refugees,” Kilicdaroglu said in an address at his party's headquarters. “You have turned your own citizens into refugees. I declare that as soon as I come to power, I will send all refugees back home. Period.”

Amid rising anti-migrant sentiment in the country, Kilicdaroglu had previously said he intended to repatriate refugees within two years by creating favorable conditions for their return. Turkey is ranked as the country hosting the largest number of refugees, including at least 3.7 million Syrians.

The CHP leader also hit back at Erdogan, who had portrayed Kilicdaroglu as colluding with “terrorists” after he received the backing of the country’s pro-Kurdish party. With Erdogan controlling mainstream media in the country, analysts say that narrative seems to have resonated with nationalist voters who shied away from backing Kilicdaroglu, fearing he wouldn't be tough enough against terrorism.

“Unfortunately, an election process that should have been a democracy festival ... was overshadowed by Erdogan’s campaigns of lies and slander,” Kilicdaroglu said.

“Weren’t you the one who was sitting at the table with terrorist organizations, making secret bargains with terrorist organizations behind closed doors? I declare to all of my citizens that I have never sat down with terrorist organizations, and I will never do. Period,” he said.

He was referring to peace efforts between Erdogan's government and the Kurdistan Workers Party, or PKK, which collapsed in 2015. The PKK, which has waged an insurgency in southeast Turkey since 1984, is considered a terrorist organization by Turkey, the United States and the European Union.

Preliminary results showed that Erdogan won 49.5% of the vote on Sunday, while Kilicdaroglu grabbed 44.9%. Ogan hasn't yet endorsed Erdogan or Kilicdaroglu for the runoff, though it wasn't clear what proportion of his supporters would vote for his preferred candidate in the second round.