Far-right Umit Ozdag, the leader of Turkey, has backed Kemal Kilicdaroglu, a candidate from the opposition, for the president of Turkey.
Recep Tayyip Erdogan faces a runoff election on May 28 against a candidate from the opposition.
Mr. Ozdag said that they had decided on a plan to send millions of migrants back to their home countries within a year.
President Erdogan is the favourite to win Sunday’s vote. In the first round, he got almost half of the votes.
Mr. Ozdag, who is the leader of the Victory Party, said he had similar talks with Mr. Erdogan, but he didn’t back him because his plans didn’t include sending refugees back to their home countries.
His decision is very different from that of his ultranationalist ally Sinan Ogan, who was the third candidate for president and got almost 2.8 million votes. Ogan said earlier this week that he would back President Erdogan.
Turkey has more refugees than any other country in the world. About 3.5 million Syrians are temporarily living in Turkey. But there are a lot of Syrians living there without permission, and people from Afghanistan, Iran, and Pakistan have also moved there without permission.
In the lead-up to the second round, Mr. Kilicdaroglu has doubled down on his promise to send Syrians home within two years. He has also accused President Erdogan of letting 10 million people into Turkey. Mr. Erdogan has promised to speed up the return of one million Syrians who want to go home on their own.
An alliance of six opposition parties picked Mr. Kilicdaroglu to run for president. On May 14, Mr. Erdogan got 2.5 million more votes than Mr. Kilicdaroglu, so Mr. Kilicdaroglu needs to win over voters who either voted for Sinan Ogan in the first round or didn’t vote at all.
Mr. Ozdag said that he and the opposition challenger had decided on a seven-point plan that included sending all “refugees and fugitives,” especially Syrians, back to their home countries within a year, “in line with international law and human rights.” He said that “13 million refugees and fugitives” were Turkey’s main problem.
Prof. Murat Erdogan, who runs the Syrians Barometer, thinks that there are no more than six million refugees and illegal immigrants in Turkey.