Three days before Turks vote in crucial presidential elections, President Recep Tayyip Erdogan’s chances of securing a swift victory took a hit on Thursday when one of his challengers left the race, a move likely to benefit Mr. Erdogan’s main competitor.
The withdrawal of one of the race’s four contenders also increased the possibility that the main opposition candidate, Kemal Kilicdaroglu, could obtain a simple majority of votes on Sunday, a win that would suddenly end Mr. Erdogan’s 20-year streak as Turkey’s most prominent politician.
The simultaneous presidential and parliamentary elections will set the future course for Turkey, a major economy at the intersection of Europe, Asia and the Middle East, and a NATO ally of the United States.
Opponents of Mr. Erdogan also view the elections as a make or break moment for Turkish democracy. A win for Mr. Erdogan, they say, would enable a leader who has extended his control over much of the state to gain even more power, whereas a loss could allow for a more democratic future.
“That is the real choice we seem to be facing now: going down the road to authoritarianism or switching track and going back to democracy,” said Ersin Kalaycioglu, a professor of political science at Sabanci University in Istanbul.
The election could also alter Turkey’s foreign affairs. Under Mr. Erdogan, Turkey has pursued a nonaligned foreign policy that has unnerved its NATO allies. While Turkey condemned the Russian invasion of Ukraine and has sent aid to the Ukrainian military, Mr. Erdogan has pursued a closer relationship with President Vladimir V. Putin of Russia.
Mr. Erdogan has also hobbled efforts to expand NATO. Although Turkey eventually voted to allow Finland to join the alliance, greatly lengthening its border with Russia, Mr. Erdogan has so far refused to do the same for Sweden. Turkey has accused the Swedes of harboring Turkish terrorists. European officials have countered that Mr. Erdogan appears to be leveraging Turkey’s position in the alliance to settle political scores.
Seeking to unseat Mr. Erdogan is a coalition of six opposition parties that have backed a joint presidential candidate, Kemal Kilicdaroglu, a former civil servant. Mr. Kilicdaroglu has vowed that if he wins he will undo Mr. Erdogan’s legacy by restoring the independence of state institutions like the central bank in the Foreign Ministry, releasing political prisoners and strengthening democratic norms.
Recent polls have suggested a slight lead for Mr. Kilicdaroglu, which would likely receive a lift from the withdrawal of one of the other candidates on Thursday.
That candidate, Muharrem Ince, was predicted to win votes in the single digits, but even that could have been enough to deprive any other candidate of winning a majority, prompting a runoff between the top two vote-getters on May 28.
Mr. Ince announced on Thursday that he was withdrawing from the race after sex tapes that supposedly showed him in compromising positions surfaced on social media. Mr. Ince dismissed them as fakes, but withdrew from the race nevertheless. He did not endorse another candidate, but pollsters said voters who would have voted for him were more likely to choose Mr. Kilicdaroglu over Mr. Erdogan.
Since the ballots have already been printed, Mr. Ince’s name will still appear at the polls.
Another candidate, Sinan Ogan, is also in the race, but his support is thought to be negligible.
Analysts caution that many Turkish polls have proven unreliable in the past, and that how this one plays out could be surprising. Mr. Erdogan remains popular among a significant share of Turks, who like his nationalist rhetoric, credit him with developing the country or simply have a hard time imagining anyone else in power.
Mr. Erdogan has also tapped state resources to increase his chances. In recent months, he has raised the minimum wage, increased civil servant salaries, changed regulations to allow millions of Turks to receive government pensions early and expanded assistance programs for the poor.
Marketing himself as a leader who has increased Turkey’s stature on the world stage, he had a Turkish-built warship parked in central Istanbul, became the first owner of Turkey’s first domestically produced electric car and observed, via video link, the first fuel delivery to a Russian-built nuclear plant near the Mediterranean.
He and his ministers have attacked the opposition as incompetent, backed by foreign powers and out to undermine family values by expanding L.G.B.T. rights.
The opposition has tried to sell voters on the prospect of a brighter future if they win, vowing to tame inflation, restore political rights and move Turkey away from what they consider one-man rule.
“This election is very important, and we have to end this autocratic, crazy system,” said Bilge Yilmaz, an economist who oversees economic policy for one of the six opposition parties. “The country deserves better, needs to do better.”