Turkey Orders New Election for Istanbul Mayor, in Setback for Opposition

“We have won this election with the sweat of millions of people. You are the biggest witness to that sweat, you are our biggest comrades,” he said in televised remarks. “You may be upset now, but don’t lose your hope. We are here. Do not give up.”

Hearing the news, citizens in some Istanbul neighborhoods who oppose Erdogan took to the streets, banging pots and pans to vent their frustration. “There is a thief here!” protesters chanted in Kadikoy, an opposition stronghold.

“I think this is the greatest distortion of democratic elections in Turkey since the country’s first free and fair polls in 1950,” said Soner Cagaptay, director of the Turkish Research Program at the Washington Institute for Near East Policy.

“This is a sad day for Turkey,” he added. “Never before has the loser in Turkey refused to recognize the outcome of an election. This decision throws into doubt hard-earned consensus in Turkey built over decades that power and government changes hands through democratic elections.”

Turkish political analysts, speaking on condition that they not be named for fear of retribution from the palace, said Mr. Erdogan had been furious at the loss of Istanbul.

By one account, he threw a tantrum on the night of the election, which was ultimately decided by a margin of 13,000 votes.

According to another account, the ruling party’s candidate, Yildirim, a former prime minister and close ally of the president, was ready to cede the election but was stopped at the last minute and made to declare victory, most probably by Erdogan himself.

As electoral officials prepared to certify that Imamoglu had narrowly won, the president and his party alleged irregularities so broad that they took the extraordinary step of petitioning for the election to be held over.

Mr. Erdogan’s party made its last-ditch appeal on the grounds that banned officials and voters had taken part in the election and that thousands of names had been dropped unlawfully from the electoral rolls.

The proof they offered was far from overwhelming — mainly focused on allegations of a conspiracy — and many of those allegations were dismissed by the 11 judges of the High Election Council.

But Monday’s decision indicated that the judges had accepted the allegations that some polling station officials were not appointed from among public officials, as required under Turkish law.

The decision was 7 to 4 in a body whose independence has been questioned by the opposition since the judges’ terms were extended for another year at the end of 2018 in an amendment put forward by Mr. Erdogan’s party.

Recep Ozel, the A.K.P.’s representative to the election council, said that Imamoglu’s mandate was now canceled and that the Interior Ministry would appoint an interim mayor until the rerun.

The opposition had proved itself seemingly well organized for the March 31 vote, stationing supporters to monitor the count in every polling station.

Once challenged, Imamoglu, the opposition candidate, insisted he was ahead and had the documentation to prove it.

There followed a flurry of conflicting messages and political maneuvering from Mr. Erdogan’s camp as the leadership played for time.

Mr. Erdogan himself at times seemed to be ready to concede, amid warnings in Turkey and abroad that, if he tried to cancel the election, the ensuing political turmoil would risk a deeper economic crisis.

Behind the scenes on election night and the days that followed, a fierce power struggle was unfolding between a tight circle of ambitious, hawkish officials around the president who were determined to hold on to Istanbul, and a wider circle of older heads in the party who advised acknowledging defeat in the city.

In the end, Erdogan decided to fight the humiliating results.

“With the influence of those circles around him that I identified as a group, he made himself believe that he might get results with the appeal process,” said Abdulkadir Selvi, a columnist known for his close contacts in the government.

That group is believed to be led by Erdogan’s son-in-law, Berat Albayrak, 41, who was promoted to minister of finance and treasury last year. The interior minister, Suleyman Soylu, 49, has also emerged as an aggressive player.

Erdogan never went as far as claiming victory, but he did play for time, and he and his allies immediately began trying to reverse the outcome in Istanbul.

The morning after the election, the judge heading the High Election Council confirmed that Mr. Imamoglu was indeed ahead in the race, but the count dragged on and was only completed two days after the election.

Officials of the ruling party then issued a deluge of objections and appeals across Istanbul’s 39 districts to challenge the numbers. Recounts were ordered in five districts and invalid ballots examined and recounted across all districts.

Politicians, party supporters and analysts feverishly followed every recount, claim and counterclaim. The gap between the candidates narrowed bit by bit.

The opposition-run district of Buyukcekmece became a focus. An A.K.P. official announced that two people from the district had been arrested. They included a municipal worker in the census office who had removed more than 3,000 people from the electoral rolls.

Altogether, the worker had made 7,000 irregular entries by registering people in nonexistent or half-built properties, or by adding them to buildings that were already occupied.

Imamoglu derided the claims, saying that in fact the A.K.P. had been found to be behind several efforts to register people illegally in the district. More than 700 people were removed from the electoral roll by election officials during the formal registration process earlier in the year, opposition officials said.

Ten days into the process, with the numbers still not showing in his favor, Erdogan said that the irregularities had been organized and criminal and that the election should be canceled. Pro-government newspapers picked up the cry.

After that, Erdogan held a meeting of his party administration, which was leaning toward applying for cancellation, according to Selvi, the columnist.

Ali Ihsan Yavuz, deputy chairman of the A.K.P., delivered three suitcases of documents to the High Election Council and gave an hours-long briefing to reporters with a PowerPoint display.

There had been forgery, fraud and unlawfulness, he said.

Nine ballot-box officials had been purged from their public posts, so their appointment as election officials was unlawful, he said, adding that the government was deepening its investigation around the two people arrested in Buyukcekmece in connection with registration and census irregularities.

He suggested that officials purged in the extensive government crackdown since the failed coup of 2016 should not be allowed to vote. A further complaint claimed that 41,000 ineligible voters may have voted unlawfully.

“There is fraud here, corruption,” Mr. Erdogan told an assembly of businessmen on Saturday. “Removing this corruption, this fraud will exonerate the High Election Council, and also fill our nation’s heart with peace.”