Voting for Turkey’s presidential runoff election between incumbent Tayyip Erdogan and his rival Kemal Kilicdaroglu, who wants to terminate the president’s two-decade rule, started on Saturday among Turkish residents residing overseas.

On May 28, Turkey will hold a runoff election after Erdogan narrowly missed the 50% barrier required to win the presidential vote outright last Sunday in what had been anticipated to be his biggest electoral threat ever.

Some 3.4 million Turks are eligible to vote abroad, out of a total electorate of more than 64 million, and will cast their ballots from May 20-24.

State-owned Anadolu news agency said voting had started in countries across Asia and Europe. Germany is home to the world’s largest Turkish diaspora, where there are some 1.5 Turkish citizens eligible to vote.

In last Sunday’s vote, Erdogan’s ruling AK Party and its nationalist allies won a comfortable parliamentary majority.

Kilicdaroglu, candidate of a six-party opposition alliance, won 44.88% support in the presidential election, trailing Erdogan on 49.52% and confounding expectations in opinion polls that the challenger would come out ahead.

Attention is now focused on nationalist Sinan Ogan, the candidate who came third with 5.17% support. Any decision by him to support one of the two candidates in the runoff could potentially have a decisive role.

Kilicdaroglu’s rhetoric has taken a nationalist turn after he trailed Erdogan in the first round of voting, saying that the government had allowed 10 million refugees into the country and that he would repatriate them all if he were elected.

He provided no evidence regarding the number of migrants. Turkey hosts the world’s largest refugee population of around 4 million, according to official figures. Ogan had campaigned on sending back migrants, including some 3.6 million Syrians displaced by war to the south.

Erdogan says only he can ensure stability in Turkey, a NATO member state, as it grapples with a cost-of-living crisis, soaring inflation and the impact of devastating earthquakes in February.