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 per cent 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 campaign.

This week, however, the 74-year-old politician hardened his rhetoric in an apparent effort to appeal to nationalist voters. “Erdogan! You did not protect the borders or the honour of the country. You brought in more than 10 million refugees,” Kilicdaroglu said.